The first thing you should consider is the facility itself. I recommend that you take a tour of the facility, and your child should come too! How do you feel when you enter the preschool? Do you feel welcomed? Does your child like it? Look around at the artwork on the walls, the toys in the bins. Do the kids look like they are having fun there? Does it seem organized and clean?
Perhaps the most important part of the tour involves the teachers. Take some time to chat with the director and meet the staff. Do they seem knowledgeable? Do they feel approachable? Are the children interacting with them? Ask whatever questions you want. No question is too silly or too small. Every parent has different issues, concerns or thoughts on what they want their child to get out of preschool. A good Director and staff will welcome your questions and be happy to discuss your child and their specific strengths and areas for them to grow.
Remember, not every preschool will be able to meet every need. It is a very personal fit, one that you have the luxury of choosing. I always tell my families to go with what they feel in their heart is best for their child and their family. They are very rarely wrong :)