Mr. Jaggers is Pip's guardian, Miss Havisham's lawyer, and he really knows his stuff. He's exactly like Billy Flynn: he ALWAYS wins his cases. Judges and juries alike quiver in their boots when Jaggers takes the stage.
With minor characters like Jaggers, Dickens takes it easy on us: you can almost always tell what you need to know based on their looks. So let's take a look at Jaggers the first time Pip meets him on the stairs at Miss Havisham's:
He was a burly man of an exceedingly dark complexion, with an exceedingly large head, and a corresponding large hand. He took my chin in his large hand and turned up my face to have a look at me by the light of the candle. He was prematurely bald on the top of his head, and had bushy black eyebrows that wouldn't lie down but stood up bristling. His eyes were set very deep in his head, and were disagreeably sharp and suspicious. He had a large watch-chain, and strong black dots where his beard and whiskers would have been if he had let them. (11.39)
This is… well, to be honest, this one is hard to read. Is Jaggers a good guy or a bad guy? In fact, he's kind of neither. He does some bad things, like getting criminals off, but he also gives Estella to Miss Havisham because he thinks he might be able to save her from a life of crime, and he's really enamored of the truth: "Take nothing on its looks," he tells Pip in maybe the best piece of advice the poor boy ever gets: "take everything on evidence. There's no better rule" (40.92).
One more things about Jaggers: his hands always smell like soap, and he washes his hands constantly, like he's trying to wash away the grime, the corruption, and the horrors of those he works with everyday.