Here is a list of questions you may like to answer about your character. Even experienced roleplayers may come across some questions they've never thought of. For an example of how to fill this out, I did mine in an interview format here.
Fill out as much as you feel like, but I suggest you fill out at least 2 parts, including the Basics.
Part 1: The Basics
1. What is your full name? Do you have any nicknames?
2. Where and when were you born?
3. Who are/were your parents? (Know their names, occupations, personalities, etc.)
4. Do you have any siblings? What are/were they like?
5a. Where do you live now, and with whom? Describe the place and the person/people.
5b. What part of your home do you like best? Least?
5c. What do your sleeping quarters look like? What do you sleep in? Any recurring or particularly strong dreams?
6. What is your occupation?
7. Write a full physical description of yourself. You might want to consider factors such as: height, weight, race, hair and eye color, style of dress, and any tattoos, scars, or distinguishing marks.
8. To which social class do you belong?
9. Do you have any allergies, diseases, or other physical weaknesses?
10. Are you right- or left-handed?
11. What does your voice sound like?
12. What words and/or phrases do you use very frequently?
13. What do you have in your pockets?
14. Do you have any quirks, strange mannerisms, annoying habits, or other defining characteristics?
Part 2: Growing Up
15. How would you describe your childhood in general?
16. What is your earliest memory?
17. How much schooling have you had?
18. Did you enjoy school?
19. Where did you learn most of your skills and other abilities?
20. While growing up, did you have any role models? If so, describe them.
21. While growing up, how did you get along with the other members of your family?
22. As a child, what did you want to be when you grew up?
23. As a child, what were your favorite activities?
24. As a child, what kinds of personality traits did you display?
25. As a child, were you popular? Who were your friends, and what were they like?
26. When and with whom was your first kiss?
27. Are you a virgin? If not, when and with whom did you lose your virginity?
28. If you are a supernatural being (i.e. mage, werewolf, vampire), tell the story of how you became what you are or first learned of your own abilities. If you are just a normal human, describe any influences in your past that led you to do the things you do today.
Part 3: Past Influences
29. What do you consider the most important event of your life so far?
30. Who has had the most influence on you?
31. What do you consider your greatest achievement?
32. What is your greatest regret?
33. What is the most evil thing you have ever done?
34. Do you have a criminal record of any kind?
35. When was the time you were the most frightened?
36. What is the most embarrassing thing ever to happen to you?
37. If you could change one thing from your past, what would it be, and why?
38. What is your best memory?
39. What is your worst memory?
Part 4: Beliefs And Opinions
40. Are you basically optimistic or pessimistic?
41. What is your greatest fear?
42. What are your religious views?
43. What are your political views?
44. What are your views on sex?
45. Are you able to kill? Under what circumstances do you find killing to be acceptable or unacceptable?
46. In your opinion, what is the most evil thing any human being could do?
47. Do you believe in the existence of soul mates and/or true love?
48. What do you believe makes a successful life?
49. How honest are you about your thoughts and feelings (i.e. do you hide your true self from others, and in what way)?
50. Do you have any biases or prejudices?
51. Is there anything you absolutely refuse to do under any circumstances? Why do you refuse to do it?
52. Who or what, if anything, would you die for (or otherwise go to extremes for)?
Part 5: Relationships With Others
53. In general, how do you treat others (politely, rudely, by keeping them at a distance, etc.)? Does your treatment of them change depending on how well you know them, and if so, how?
54. Who is the most important person in your life, and why?
55. Who is the person you respect the most, and why?
56. Who are your friends? Do you have a best friend? Describe these people.
57. Do you have a spouse or significant other? If so, describe this person.
58. Have you ever been in love? If so, describe what happened.
59. What do you look for in a potential lover?
60. How close are you to your family?
61. Have you started your own family? If so, describe them. If not, do you want to? Why or why not?
62. Who would you turn to if you were in desperate need of help?
63. Do you trust anyone to protect you? Who, and why?
64. If you died or went missing, who would miss you?
65. Who is the person you despise the most, and why?
66. Do you tend to argue with people, or avoid conflict?
67. Do you tend to take on leadership roles in social situations?
68. Do you like interacting with large groups of people? Why or why not?
69. Do you care what others think of you?
Part 6: Likes And Dislikes
70. What is/are your favorite hobbies and pastimes?
71. What is your most treasured possession?
72a. What is your favorite color?
72b. What style of clothing do you prefer?
73a. What is your favorite food?
73b. What is your favorite smell?
74. What, if anything, do you like to read?
75. What is your idea of good entertainment (consider music, movies, art, etc.)?
76. Do you smoke, drink, or use drugs? If so, why? Do you want to quit?
77a. How do you spend a typical Saturday night?
77b. What type of transportation do you prefer?
78. What makes you laugh?
79. What, if anything, shocks or offends you?
80. What would you do if you had insomnia and had to find something to do to amuse yourself?
81. How do you deal with stress?
82. Are you spontaneous, or do you always need to have a plan?
83. What are your pet peeves?
Part 7: Self Images And Etc.
84. Describe the routine of a normal day for you. How do you feel when this routine is disrupted?
85. What is your greatest strength as a person?
86. What is your greatest weakness?
87. If you could change one thing about yourself, what would it be?
88. Are you generally introverted or extroverted?
89. Are you generally organized or messy?
90. Name three things you consider yourself to be very good at, and three things you consider yourself to be very bad at.
91. Do you like yourself?
92. What are your reasons for being an adventurer (or doing the strange and heroic things that characters do)? Are your real reasons for doing this different than the ones you tell people in public? (If so, detail both sets of reasons...)
93. What goal do you most want to accomplish in your lifetime?
94. Where do you see yourself in 5 years?
95. If you could choose, how would you want to die?
96. If you knew you were going to die in 24 hours, name three things you would do in the time you had left.
97. What is the one thing for which you would most like to be remembered after your death?
98. What three words best describe your personality?
99. What three words would others probably use to describe you?