Start with a PHYSICAL DESCRIPTION of your character. Does he or she have any unique identifying marks, tattoos, scars, etc.? Nail polish color is part of the description, as is hair style, type of clothing and accessories the character wears. Don't forget the bling! What kind of jewelry is your character wearing?
Describe the kind of VOICE your character has. Is it whiny, nasal, high or low pitched? What kind (if any) of accent does he or she have? Does your character talk like someone who is educated or someone who likely did not finish the third grade? Voice tells the reader a lot about the character, so be sure to pay a lot of attention to this part of the sketch.
What does your character DO FOR A LIVING? Is he or she old enough to have a job? What kind of job? Is he or she happy with the job? If your character is a child, what does he or she pretend to be during play? My six-year-old granddaughter thinks she is a cat, in fact the other day she told me she was part cat, part human, and part duck.
What are your CHARACTER'S THOUGHTS ON LIFE? Does he or she go to church? Vote? What party? How far did he or she go in school? What does he or she think about the current state of affairs? (This should coincide with the time frame in which the story is set.)
How does your CHARACTER INTERACT WITH OTHERS? Do others like her or him? Why or why not? Think of both work and personal relationships here. Is your character well loved at work, but a tyrant at home?
What are your CHARACTER'S MAIN INFLUENCES IN LIFE? Who does he or she trust with secrets or sensitive information? Who does the character look up to for inspiration, support, or advice? Why?
WHERE DOES THE CHARACTER LIVE? Not just the country, state, county, city, but also the neighborhood, the street, what kind of house? Does the character pay rent? Have a mortgage? Live with his/her parents, spouse, children, roommates, or live alone? Are there pets?
Finally, determine WHAT KIND OF PERSON THE CHARACTER IS. Is he kind, mean, or grumpy? Does she like herself? Is he confident, is she driven or laid back?
Once you have written your character sketch, sit back and think about the character, get to know him or her in your mind so when you introduce him or her in the story, you are introducing someone you know very well.