Share my experience:

We used Yahoo yellow page and find about 10+ preschool candidates in 5 miles range around my home. Then we visit them one by one. There are big differences between them in terms how good facilities is, how good the mangement (communication and altitude) is, how good the order is maintained in site, currilucum, and if the lunch is provided. Finally I found three. One is in waiting list, one is too expensive, and we finally pick one and that is a happy ending.