Can you answer me these riddles three?
Do you know what you like, I mean really like, in a roleplaying game? It can be really tricky to pinpoint just what it is that a person enjoys and, of course, it's best not to be too rigid about it. I've had a man who declared himself a proud power gamer who was only after better statistics and never cared much about roleplay, throw himself into a World of Darkness game that, admittedly had plenty of action, but also had plenty of character-defining moments, investigations, and strange horrors to flee. Also, what are the little bits and pieces that you tend to enjoy in a game. Equipment management, commerce, gang warfare, territory expansion, having a real impact on your local community, getting to betray others, working against the other PCs, complex interplay between morally ambiguous courses of actions, morally simply fun and frivolity, lively taverns. Anything really.
Hell, if you're not TOO sure, then it's just as good (some might say better) to just make a point to tell the GM which parts you enjoyed the most. It works like classical conditioning and you're bound to see more like it.
Do you know what your trigger points are for irritation or anger, for better or worse, in house rules, NPCs, and plots? Your trigger points could involve things you don't want to involve in any game, perhaps homophobia or misogyny or child abuse, or it could involve things that you like to attribute to enemies because it'll really get you fired out and keen to kill the villains. My fiance hates hypocrisy, especially self-entitled hypocrisy, and he respects more honest villains, so if I want to push his buttons with a villain, I just make them proudly hypocritical and thinking they're doing the right thing. If I want him to think they're cool, or even admire them, often just having the villain admit to his villainy helps settle him down (obviously it matters what the villain's doing).
Do you know what you enjoy spending the session doing? This one is vital. There's nothing so irritating as a GM then when a player is really not enjoying the game because of a poor choice of character. When the confirmed action hero plays a socialite who hates getting their hands dirty and then gripes that the game is dull. Or when the player, all fired up about an investigative game due to their interest in crime scene investigation, plays a lazy cop always eager to turn a blind eye and then complains they feel unmotivated.
Repeat after me: My character is a protagonist and my lens into the game.
As any good novelist or screen writer will tell you, you shouldn't make your protagonist in a vacuum, or else no matter how much you love the genre, you may well trample all over it. Consider the game, the game world, and what you want to spend your time doing, and then select a character based around that.
Knowing yourself, what you want, what you enjoy, and what you dislike is vital so you can communicate that to the Game Master. Otherwise, don't complain if the game seems to be developing in ways you really don't enjoy.