The world's first democracy developed in Athens at the same time that Athens was growing increasingly imperial.
The basic outlines of the development of democracy run from Solon to Cleisthenes to Ephialtes to Pericles.
Solon laid the basis for democracy through eliminating debt slavery. He also probably established the Council of 400. Also, he gave every citizen the right to appeal the verdicts of magistrates before the assembly. He is sometimes credited with introducing sortition as well, but that is doubtful. It would be utterly inaccurate, however, to call Solon a democrat. He helped the people, but was fundamentally aristocratic. He divided Athenians into four census classes, the Pentecosiomedimnoi, the hippeis, the zeugites, and the thetes. I.e. the Rich, the Knights, the Hoplite-class, and the Lowest class. Most offices were restricted to the upper classes, with the thetes having virtually no official role, not least because they could not afford to take time off for public service.
Cleisthenes, an Alcmaeonid like Pericles, furthered democracy first by ousting the Pisistratid tyrant Hippias (with Sparta's help), and more so by a series of reforms. Cleisthenes' reforms are so clearly designed to increase the people's power that he can be described as a true democrat.
First, he established administrative units called tribes made up of thirds. Each third was from a different area of Attica: city, hills, and coast. Each third was made up of demes. Think of a deme as a village or a neighborhood in the case of the city: the fact that the demes were already existent units made Cleisthenes' reforms more palatable (so the theory goes) and contributed to the long life of Cleisthenes' reorganization. Cleisthenes' reform made Athenians belong primarily to a unit that was spread around Attica. Hence it was more difficult for influential families to build up geographical power-bases. In spite of that, Athens remained essentially aristocratic and plutocratic.
Each new tribe had a statue in the agora, a shrine, property to raise revenue, and was organized to provide a quota of men for the military as well as civic offices.
Cleisthenes may also have increased the citizen body by including landless thetes as well as land-owners.
He created a Council of 500 in place of the Council of 400. This was a probouleutic council.
The Lot, or sortition, may have been introduced by Cleisthenes in 508/7, but by 487, there was a prelim election followed by a selection by lot.
The ten tribes provided a general apiece.
As time went on, Cleisthenes was more and more ignored by Athenians, while they portrayed Theseus and Solon as their democratic founders.
Cleisthenes had a rocky start in Athens. First, he machinated to oust the tyrant Hippias. Then when he was ousted, Cleisthenes faced a rival, Isagoras. He lost out to Isagoras at first, when Isagoras was elected eponymous archon for 508/7, but he carried his reforms thru the assembly anyways. Isagoras responded by calling on the Spartan Cleomenes. Cleomenes demanded that Cleisthenes leave Athens because of the very old curse on the Alcmaeonids because of their role in murdering the followers of Cylon, a would-be tyrant from an earlier age in Athens. Cleisthenes left Athens, Cleomenes came to Athens and demanded that the council of 400 be abolished and tried to put Isagoras in power. When the council refused, Cleomenes took possession of the Acropolis. The people besieged the acropolis in anger, and Cleomenes withdrew. The Athenians recalled Cleisthenes and his supporters, and Cleisthenes' reforms went ahead. It was probably easier for him to carry thru his reforms at that point because Isagoras and his supporters had either fled or were in disrepute. In 506, however, Cleomenes tried to attack Athens again, aided by Thebans from the northwest and Chalcidians from the northeast. The campaign fell apart, but it shows the opposition to Athenian developments. In the north, the Athenians defeated the Chalcidians and Thebans and established an Athenian garrison to keep watch on their north.
How things actually worked in the early 5th century is not clear. There was the Areopagus, the Council of 500, and an Assembly of the people (ecclesia). Although the people technically apparently had full power, they were slow to use it. The Areopagus had a lot of power, presumably.
The board of generals worked by rotation (at Marathon, each general was commander of the whole army for a day in rotation) of some sort and by consensus. They had financial roles as well as foreign policy roles in addition to military. Because they were elected for ability and could stand for office year after year, they were the most important officials in many ways.
The Council of 500 was changed every year. The selection may have been by lot after a preliminary election. They came from the top three census classes. The main function of the Council was probouleutic.
The Assembly (ecclesia) was open to every citizen, including thetes. Thousands of sailors manning the fleet grew more and more aware of their political power.
Up to 462/1, Cimon, who favored cooperation with Sparta, had presumably held further democratic reforms in check. With his disgrace after the insulting dismissal by the Spartans, Ephialtes stripped the Areopagus of its powers. Later Athenians portrayed the Areopagus as a benevolent guardian of laws and supervisor of morals that was destroyed by revolutionary radicals. Whatever it was that Ephialtes did, and there is debate and limited evidence, he seems to have reduced the power of the Areopagus and correspondingly increased the powers of the Council, the Law Courts, and the Assembly. He is probably responsible for the popular courts which were to have so much power later.
Much of what we think about the running of Athens is built on knowledge from the second half of the 5th century, and the earlier period is hazy. We know that in the later half, the Areopagus was limited to homicide and religious cases, and that magistrates had to submit to examinations of their conduct in office. This may have been something of what Ephialtes instituted or laid the tracks for.
Ephialtes was assassinated, presumably by anti-democratic forces.
With Cimon ostracized in 461, and soon after he came back, dead in 450, Pericles rose to the forefront and was largely unopposed in his further reforms.
Under Pericles, what is referred to as radical democracy took shape. The assembly and the law courts had ultimate authority. No property requirement for most offices. Election was reserved for offices that required professional expertise. Much was done by sortition, also called "lot." Boards of ten (one per tribe) were common, and collegiality was the rule.
The generals remained in many ways the most important officials. They were not just military commanders, but also surely ex officio members of the council. They influenced foreign policy as well as finances. A general elected year after year could dominate domestic as well as foreign policy, but they were still subject to the assembly. If they disagreed with the assembly's decision, they would still follow it, because the people might not elect them again if they did not, and they had to face an examination of their conduct on leaving office. That in fact led some generals to be indecisive, with Nicias, the general of the Sicilian Expedition, a prime example.
At some point, the older method of selection for office was eliminated. That method had been to hold a prelim election to establish a pool of candidates, then to select one by lot. At some point in the Pericles' lifetime, two methods were used exclusively: 1) election, and 2) sortition (lot).
Also during Pericles' tenure, pay for civic service was instituted. No single other reform furthered democracy as much as pay for service. Now many more people could afford to serve, and for some, serving became attractive financially. First, dicasts, or jurors, began to be paid. A low rate, but half a day's wages or so. That was introduced by Pericles while Cimon was still around, perhaps to counteract his liberality with his own wealth. Jurors were appointed by lot annually and could serve year after year. By 422 (Aristophanes Wasps 662), there were 6,000 jurors per year. Cleon increased the pay rate to 3 obols a day. Pericles also started the payment of soldiers and sailors 3 obols a day. By 411, the councillors and archons were paid.
The archons' roles were vastly reduced: Ephialtes stripped them of the role of handing down judgements (the jury did that). Individual archons supervised religious festivals and presided over certain suits, and conducted certain religious rites. The 6 Thesmothetai (a kind of archon) had juridical duties and drew up the court calendar.
The Council of 500 (Boule) is a mystery in its early existence, but we know that later its membership was determined by lot from the whole citizen body, 50 men from each tribe each year. No one could serve more than twice. Met daily. Each Prytany, the 50 from one tribe ran the Council with one man each day being Epistates (President!). The council was deliberative, administrative, and judicial. It prepared the agenda for the Assembly and saw that the Assemblies decrees were carried out. It investigated candidates for office and was involved in their post-tenure examinations.
The Assembly met 40 times a year or more. Every citizen could attend. There was no seniority system. It elected the generals and other elected offices. This was not representative democracy. It was direct with maximum participation. It met on the Pnyx hill. Sessions began in the morning and ended at dark. Each meeting began with a sacrifice and a herald's proclamation of a curse on those who deceived the people. The agenda was set by the council and had to be posted 5 days in advance. Each item was read, followed by debate. Amendments were also possible from the floor. Direct action from the floor was also possible, but it was then directed to the Boule, who would prepare it for a later meeting of the Assembly. As each person rose to speak, he would go to the tribune, put a myrtle wreath on his head, and address the assembled people. The debate about the fate of Mytilene occurred at such a meeting and shows how it worked. The Assembly received foreign delegations, decided on war and peace, size of military expeditions, dispatched colonies and cleruchies, decided on building new temples etc., and supervised state finances and the food supply.
All elected officials had to undergo a dokimasia, or proofing, prior to taking office, and an examination after their term. Even the council, at the end of the year, was subject to an examination and would get a golden crown for dedication in a shrine if they did well.
There were many boards of ten, who were appointed by lot and served for a year. Each board would have limited jurisdiction and was supervised and charged by the Council.
In each prytany, 10 auditors selected by lot examined the books of financial magistrates.
10 investigators appointed by lot considered complaints which any citizn made about another citizen's conduct in office and decided whether to refer the matter to a court.
There were treasurers of Athena, who were exclusively from the pentecosiamedimnoi, who were in charge of the treasury but also made loans to the state.
There were officials called poletai who held auctions for contracts to collect taxes and work the mines as well as for confiscated goods.
The Eleven were in charge of the prison and executions.
Board of 10 in charge of the temples.
Board of 5 in charge of roads.
10 city commissioners supervised female entertainers and made sure houses did not encroach on roads and dung collectors dumped it over a mile from the city.
Grain wardens, Market superintendants...
All of the runnings of the Athenian government was furthered by public slaves, who could help the new officials each year know what to do. The police force consisted of slaves.
In Pericles' time, there were probably between 40 and 50 thousand adult male citizens. There were perhaps 30,000 metics, and 100,000 slaves. Children? Women?
The young men 18-19 spent so much time in military service that they probably did not serve in government.
While anyone could theoretically propose anything, in reality, the more powerful were recognized, and those who knew how to do things got further. One's speaking ability was the key.
In 399 a law was passed which said that "no decree, whether of the boule or of the people is to have more authority than a law." The distinction is not clear, but a law is a longstanding more general law, while a decree is usually passed for a particular occasion. The "laws" of Solon or Cleisthenes were laws, while those from yesterday might not be laws.
There was a provision that any citizen could bring a suit against another, called a graphe paranomon, claiming that a measure initiated in the boule or assembly was illegal. The proposer was free from prosecution for doing so for a year after he brought the charge. The trial took place before 1000 jurors. If one did not receive 1/5 of the votes, one was fined and barred from further such suits.
There was also a provision that one could bring forth a proposal that was illegal if one first obtained adeia (immunity).
There was provision for impeachment (eisangelia).
Any citizen could bring a suit (a "probole") in the assembly against another for acting against the interests of the state. If the assembly agreed, a trial before a law court was held.
In fact, the assembly was a bit too zealous: many magistrates failed to act out of fear of the examinations.
Under Ephialtes and Pericles, the court system was greatly expanded. Jurors came to be the primary decision makers, with magistrates simply presiding.
Prosecution was left to volunteers: there were no official prosecutors. "Sycophant" was a term for those who tried to profit by prosecuting (measures were taken to discourage sycophancy). Sometimes, there were officially appointed prosecutors (Pericles was appointed to prosecute and impeach Cimon in 463).
Court actions were divided into private (dike) and public (graphe). A dike could be initiated only by the parties directly concerned or their legal reps. A graphe could be initiated by any citizen. Homicide was a dike, not a graphe. Only family members could bring charges.
It was a good way to rise to power to prosecute a famous case. Sometimes prosecutors got a share of the fine.
Trials lasted one day.
Men had to speak for themselves in trials. A class of professional speechwriters arose who wrote speeches for others.
Voting was done using pebbles and later with special disks.
After conviction, the prosecutor proposed a penalty, then the defendant proposed a counter-penalty. The jury decided between the two, but could not suggest something else.
Execution was one possible penalty. There were three methods: barathron (being hurled from a high place into a pit filled with stakes and spikes), apotympanosis (being chained upright to a plank and being left to die [or perhaps being strangled by tightening the neck band gradually]), and hemlock (a rather pleasant death, relatively speaking).
Athenian government had various sources of revenues, including the mines as laurium, public lands, and taxes. Direct taxes on citizens were not the norm, but metics were taxed every year, as were imports/exports, prostitution, and the law courts brought in revenue from fines and confiscations.
"Liturgy" was the name for the institution by which rich Athenians were made to contribute. They had to support a trireme, a chorus for a tragedian, etc. as a "liturgy."
Metics were resident foreigners. They brought wealth, labor, and cultures to Athens. They were allowed to introduce many of their native gods, which were then worshipped by many Athenians: Thracian Bendis, Anatolian Cybele, Syrian and Cypriot Adonis, Egyptian Isis.
Also, intellectuals flocked to Athens: Anaxagoras of Clazomenae, Hippodamus of Miletus, Protagoras of Abdera, Polygnotus of Thasos (painter), Aristotle of Stagira, Theophrastus of Eresos.
Metics were rarely made citizens.
Slaves were ubiquitous. Chief source was war. The majority were barbarians, but there were Greek slaves too. Slaves were an investment for some, and they could be rented out. The mines at Laurium were hell on earth for the 20-30 thousand slaves who worked there. The Scythian Archers were about 300 slaves who formed the police force of Athens. Many slaves were government clerks. The Greeks were largely unreflective about slavery and freedom: the development of Athenian Free Democracy was built on a slave-owning culture.