Plato’s dialogues are generally sliced into three periods, although not everyone agrees which dialogue goes where. It’s generally considered that in the early dialogues, Plato really was acting largely as a stenographer and these are more-or-less accurate accounts (albeit written by an admirer) of Socrates walking around Athens and taking the piss with the prominent figures of the town.
During this period, the character of Socrates, probably like the real Socrates, interrogates people to get them to analyze whether they’re living in a morally appropriate way. Socrates’ touchstone was that “the unexamined life is not worth living,” so he forces the citizens to examine their lives in this way. He does this via the Socratic Method – asking questions and then ferreting out the contradictions implicit in his subject’s answers (he also does a lot of totally unfair equivocation*) with the result that his subjects often find themselves arguing against their own position. Socrates claims that he never introduces any new arguments during these sessions, merely analyzing his subject’s views, but that’s not really true. I’d say the early dialogues focus largely on morality, and in particular the morality of living the unexamined life.
During Plato’s middle period, the character of Socrates behaves less like (we think) the real Socrates did; he’s more a voice for Plato’s own philosophy, which includes both ethical principles and metaphysics. The Repulic is the largest and greatest of these works, and it’s where Plato (through his Socrates character) sets out his famous theory of the forms (in which he postulates – this is a huge oversimplification – that everything we encounter is an imperfect reflection of an ideal version of the thing which exists outside the material world).
Plato’s late period is, IMO, kind of an extension of the middle period. Here, the voice is exclusively Plato’s (although still named Socrates in some dialgoues – in others Soc. is absent) and the works lay out and revise Plato’s philosophy. (This is a far cry from the Socrates of the early dialogues, who claimed never to add arguments, but merely to deconstruct those of his subjects.) I seem to think that the late dialogues are almost exclusively metaphysics, but my experience with them is about 20 pages of the Parmenidies about 10 years ago, so take that with a grain of salt.
I’d suggest you confine yourself, in the beginning, to the early dialogues. (Crito, Euthyphro, Gorgias, Lysis, etc.) Socrates is an enjoyably irascible character in these works and because of the ethical focus and the deconstructive approach they’re a lot easier than the later works. Once you’ve got them under your belt you’ll be ready to tackle the later, more complex dialogues. Then you can shoot for Aristotle – and if you think Plato is hard to grok, you ain’t seen nothing yet!
–Cliffy
*To the philosopher, “equivocation” means switching from one meaning of a word to another, either in order to falsely trap your rhetorical opponent, or because you don’t realize the word can mean two different things. For instance, one character in the Republic essentially says that morality is a plot by the weak to keep the strong in check. Socrates then asks how the weak could impose their yoke on the strong, if the are truly weak. But it’s clear that “strong” is being used in the first sense to mean physically or martially strong, while the physically weak are tricksy, whereas Socrates pretends that strong means superior and weak means inferior, no matter the context.