They should not need a nap, be able to leave their parents without becoming overly upset, know how to dress themselves, and be able to go to the bathroom unassisted.
If your child meets these suggested readiness milestones and is five years old (or the minimal age requirement for your school district), then they are ready for the brave new world of kindergarten.
If not, fear not. Its perfectly fine to wait a year, but please talk with the school and/or your pediatrician about the need to wait until your child is older.
Hopefully tips like this will help you go to the head of the class when it comes to making sure your child is ready to embark on the great adventure of kindergarten.