I almost always start with class, as I try to form balanced parties (or, at least, not terribly unbalanced). If no one wants to be the healer, I'll step in. If everyone else wants to play martial characters, I'll play the wizard. This also gives other players a chance to try something new, e.g., warlock. I can have fun with any class, so it makes sense to let others choose first and I'll fill in the gap.