Perhaps it's the writer in me, but when the
GM hands you a freshly-printed character sheet- printed on copy machine paper as
naked as the day it was born- it's like witnessing the birth of a child.
Not just any random baby, mind you, but someone who's asked you to be a
godparent. You have a chance to shape the destiny of someone beyond the simple numbers denoting their
strength, their
speed, their capacity to think quickly, their skill with a
pen or a
gun... did he have find God and subsequently
Awaken to discover what the true nature of
magic is? Did she kill
the man that slew her father or is he still on the run from the law? When his son decided to join a group of
anarchist terrorists, did he try and persuade him not to go, or did he let his firstborn do as he pleased?
Ultimately, though, the game that the
character sheet was written for and the playing style of your
GM are going to be the greatest limitations on what comes into play. For a good ol' fashioned
3rd Edition D&D dungeon crawl, it's not going to matter much if your sister tried to assassinate the
king. In
World of Darkness games, on the other hand, the game will tell you to define what time of day and how large the knife she used was when someone asks you about it. Granted, these are both extremes, but if you ask me,
it's difficult to have too much backstory as opposed to too little.