Tools of Characterization
Well, let's see. Tartuffe is a hypocrite, a thief, a liar, and a lecher (you might call him a lady's man if he were actually smooth). In every scene of the play his actions confirm these aspects of his character. Orgon is tricked again and again by Tartuffe, showing that the patriarch is pretty gullible. Of course, Orgon also did a lot of good stuff: he served his King and put his reputation on the line in order to protect his buddy Argas.
Tartuffe loves him some good food and drink. As Dorine tells Orgon in Act 1, Scene 4, Tartuffe is "round and red,/ bursting with health and excellently fed" (1.4.6); he has no trouble putting down a "leg of mutton and a brace of pheasants [in this case a brace simply means two]" in one sitting, and he drinks "four beakers of port" at lunchtime (1.4.12, 18). Talk about a glutton.
Sex and Love
Tartuffe is similarly insatiable when it comes to loving. Even when he's set to marry Mariane – and, one supposes, benefit from the kind of "love" that happens during marriage – he also wants to sample the earthly delights of Elmire. Mariane and Valère, on the other hand, are remarkably chaste.
The characters in Tartuffe fall into three categories: upper class, also known as Orgon's family; servants, most notably Dorine; and Tartuffe gets a category all to himself. He pretends to be poor, which would put him in the lower class, but he also claims to be a former nobleman who's lost his estate, which makes him sort of upper class. What he really is, though, is a liar, a con man, and a thief. In short, he's a member of the criminal underclass.
Thoughts and Opinions
Look at it this way: Tartuffe holds a lot of opinions – about religion, proper conduct – but they're false. Orgon holds Tartuffe's opinions because he doesn't know better. Cléante has a lot to say – and we mean a lot – about, well, pretty much everything, but they're solid and well-founded. Dorine has a lot to say, pretty much all of it biting and sarcastic. And Mariane has – well, she's afraid to say anything at all.