Character creation in role playing games is the most important aspect of the hobby. In RPG's characters are what drive the story, they make all the big decisions, rescue (or imperil) the settings rulers and resources, and challenge its enemies.
The sad thing is, that many players do not bother to make their characters interesting, and so most games do not last beyond a few sessions, and fizzle out. If the players (regardless of age) put a little life into these characters, the game would be far more interesting for the DM/GM/Storyteller and the players alike. But how do you make a character unique and interesting?
Using the normal default of roleplaying games being in a pseudo-medieval world with dragons elves and dragons. Lets look at some questions that are good to ask yourself about the character to hlp you flesh out his personality and history:
Where Did The Character Come From?
Is he or she a local or a foreigner? This makes alot of difference in a medieval setting, where few people ever go farther than a few miles from where they were born. People in a medieval setting are generally very suspicious of outsiders, seeing them as inherantly immoral and suspect. DMs should feel encouraged to play this up.
What Did The Character Do Before Adventure Came Calling?
Adventurers rarely choose their careers. Often they had a normal hum-drum life before some big event, such as a rampaging enemy, plague or other event made adventuring an option (or removed all other options). Many times, and adventurer might wish nothing more than to settle down to a nice "boring" life rather than crawling through swamps and fighting monsters. Other times, adventurers might be the sort of people that never really fit in society. History is full of these sorts of adventurers including Christopher Columbus, Juan Ponce de León, Benjamin Franklin, and Jack Churchill (This guy fought in WW2 armed with a bow, arrows and a Claymore, saying: "any officer who goes into action without his sword is improperly dressed").
Career Choices: Choosing a career that the character had before adventure came a-knocking is a great way to flesh out a character and get a feel of his world view and normal skills and knowledges. An excellent list, with descriptions of medieval trades can be found here.