I agree with everything that Deborah has mentioned.
I would like to add two points. First of all, choose an area that you feel passionately about! Your enthusiasm for an area is contagious. People want to use an agent that truly knows & loves the area they want to buy or sell in.
Also see what percentage of sold homes in the area have been sold by the same realtor. You should try to avoid areas that are dominated (more than 25% of sales) by one or two individuals.