I think you will find these kid friendly behavior contracts useful in your preschool classrooms for children who need reminders to stay on task. I find the children really like having some responsibility for keeping track of the behavior that the teacher is looking for, while working towards an activity of their choice. This is a fun way for children to self-monitor behavior while producing documentation that they are making progress.
I have used the contracts for helping children to stay with an activity, complete an activity without complaining and to move through the morning activities with a desired activity as the end result.
I am including links for the (free!) favorite contracts from latitudes.org