Write the characters background as you would someone's biography. At the very least, it should answer the following questions:

• When and where were they born?
• Where they different from other children?
  • Did they have a difficult upbringing?
• What schools and institutions did they attend?
  • Did they enjoy it them?
  • Did they lean any special or unusual skill, if so how?
• What kind of person are they?
  • Do they have a mean streak?
  • Do they have a strong sense of fair play?
  • Are they religious?
  • How well do they interact with people?
  • How do they cope when things don't go the way they planned?
• What motivates them?
  • Do they go ballistic every time someone mentions the words "Cleaning Woman"?
  • Do they have a strong desire to care for lost cats?
• What do they look like?
  • What is their ethnic background?
  • Any scars or a twitch?
  • What do they like to wear?
• What do they do for a living?
  • When did they start doing it?
  • Where did they learn it?
  • How much do they earn?
• What are their hobbies and interests?
• Where do they live?
• Do they have any special possessions?
  • A weapon of some sort, a library, or an artifact?
  • Where did it come from?
  • How did they get it?
• When did they first encounter magic?
• What form does your avatar manifest in?
  • How does it get your attention?
  • Is it particularly strong or particularly weak?

Backgrounds can become quite detailed. Personally, I think this is a very good thing. I will be asking to see it.

Note: If you do not want your character to belong to a tradition then make sure your background mentions what the characters specialty sphere is.