Math centers usually have manipulatives and other materials that can easily be misplaced. In order to maintain the centers without too much work, make students responsible for the materials. Have a container with all of the necessary supplies for the math activity. Place a library card pocket (or make a simple one with heavy paper and tape) on the side of this container. Each week when you start a center, write the contents of the box on an index card and place it in the pocket. This way students can check to make sure that everything is there both when they begin and end the center activity. This should eliminate your having to prepare the center each day.