It could be my experience with WoD and White Wolf, but i always insist that the characters come up with the concept of character before ever generating stats. In some cases, when i start campaigns where the characters are children, their personality comes out, grows, and changes with the unfolding campaign. In other instances, when characters start in their late teens, early twenties... i usually bring up family background, life experiences including what brought them to become a wizard, barbarian, bard, etc. Did they have a mentor, what were they like, what influences did they bring to the table? Also to round out the character, i ask for likes, dislikes, and why, personal habits, and even mannerisms. This is all optional of course, but it does act as an effective tool to help the player visualize the pc.
'Justice, like lightning, ever should appear to few men's ruin, but to all men's fear.'