The first thing that you should figure out is the basics. These questions should be the building blocks of any good personality.
* What is your character's full name?
* Where and when were they born?
* Who are their parents?
* Do they have any siblings? If so, who are they?
* Where do they live and who with?
* What is their occupation?
* What do they look like?
* Do they have any diseases, allergies, or physical weaknesses?
* What words or phrases do they use that defines them?
* Do they have any quirks, strange mannerisms, annoying habits, or other characteristics that are specific to them.
Now that we have our basic building blocks for our character, our next step is to describe their history. It is our history that defines who we become. Because of that, we need to know what happened to our character in the past.
* How would you describe the character's childhood in general?
* What is their earliest memory?
* What was their school like and how did they like it there?
* Where did they learn the skills and abilities that they most use in the present?
* When growing up, did they have any role models?
* When growing up, how did they get along with their family?
* What did they want to be when they were a child?
* When they were a child, were they popular? What were their friends like?
* When was their first kiss and who with?
* Who was their first love?
* Are they a virgin, and if not, when and with whom did they lose their virginity?
* Describe any influences in their past which led them into becoming the person that they are today.
* What do they consider to be the most important event of their life so far?
* Who has had the most influence on them and why?
* What do they consider to be their greatest achievement?
* What is their greatest regret?
* Do they have a criminal record of any kind? If so, why?
* What is the most embarassing thing that has ever happened to them?
* What is their best and worst memory?
The next thing that we need to work on is our character's beliefs. Now we are getting into the closest parts of their soul.
* Are they an optimist or a pessismist?
* What is your character's greatest fear?
* What is their religion?
* What are their political views?
* What are their views on sex?
* What are their views on violence and killing?
* What do they feel is the most evil thing that a human being could do?
* What are their views on true love?
* How honest are they?
* Are they biased or prejudiced in any way?
* Is there anything that they would simply refuse to do no matter what the circumstances?
* Is there anyone or anything that they would die for?
Now let's move on to more matters of the heart. It's time to start exploring our character's relationships.
* How do they treat others in general?
* Who is the most important person in their lives and why?
* Who is the person that they respect the most and why?
* Who are their friends?
* Do they have a spouse or a significant other?
* Have they ever been in love?
* What is their ideal mate?
* How close are they to their family?
* Do they have children? If not, do they want them?
* Who would they turn to for help?
* Do they trust anyone to protect them? If so, then who?
* If they suddenly went missing, who would come looking for them?
* Who is the person that they hate the most?
* Do they tend to argue with people or avoid conflict?
* Do they tend to take on positions of leadership?
* Do they like interacting with large groups of people?
* Do they care about how others think about them?
So now we have come to the last part of our character, the little things that help us define who they really are.
* What is their favorite hobbies and pastimes?
* What is their most treasured possession?
* What is their favorite food?
* What is their favorite color?
* What do they do for entertainment?
* How do they deal with stress?
* Do they tend to plan things out, or do they tend to be more spontaneous?
* What are their pet peeves?
* What is their greatest strength?
* What is their greatest weakness?
* If they could change one thing about themselves, what would it be?
* Are they an introvert or an extrovert?
* Are they organized or messy?
* What things do they consider themselves good at?
* What things do they consider themselves terrible at?
* Do they like themselves?
* What goals do they hope to accomplish in their lifetime?
* Where do they see themselves in 5 years?
* What is the one thing that they want to be remembered for after they die?
Remember, these questions are meant to be a jumping point for your character, not the only things that you should answer. Each question can lead to an explaination that should help you move on to more in depth questions that are specific to your character. Usually, these answers will come up in your plots.
Just remember: be creative and have fun! That is the most important thing when writing! Good luck!