Here's a few last tidbits about my centers.
1. I keep all the centers in the cart. The students pull out the drawers and take them anywhere there is open space. The students know that they cannot be in the area as another group.
2. Centers have a limit of 4 people per center.
3. Students may only change centers if all work in their current center is finished.
4. All work must be kept in their folder and is only removed by me.
5. As much as I wanted to pull small groups for guided math time, I forced myself to monitor and correct behavior first. Procedures had to be followed before I could do this.
While the centers still aren't 100% perfect, this system works much better for me.