I have each center in a bin instead of keeping them out at all times. That way the hcildren know if they are last at the center it is their job to put things away. I also find it makes it easier when I have a sub so I can say the sticekr story center is in the red bin, etc. The only center that is always out is writing, because it has its own table with a "mail" organizer to keep paper, pictures, etc.