Some people naturally tend towards certain roles in groups they're in. Some players have a natural 'take charge' attitude, and more often than not end up being the leader. Some are more open to conversation and wit and like to play the face. Some like to sit back quietly and support the group. Others are there more for the social aspect, so their characters end up doing little outside of combat. None of these are a bad thing, but it can be good to know which you are.
I tend towards one or two camps: I tend to play someone capable of leadership - or second in command - or someone who can support the group. Sometimes supporting the group means big damage, but more often it is something like pilot/driver, engineer, medic, etc. How that works depends a lot on the character I am playing, but generally my character has the motivation to go and do things - which ends up with them being nominally in charge in some fashion - or they don't have that motivation in which case I end up more quiet.
I've taken pains in some recent games to make other types, and it's been fun, but that is where I tend to drift on my own.
How about you?