I put my kids in pairs. They got new buddies every 9 weeks. It worked best for me to do it by personality...some kids just don't work well together! I would pull my guided reading groups as I needed them.
Here's what I ended up doing by January and it worked really well. I bought different colored baskets (red, blue, green, and yellow)...2 of each color...and I put the materials for the stations in the baskets. Some baskets had some different games or options and they were loosely based around the stations Debbie Diller describes in her book...I switched out stations and materials as needed or as I wanted to focus on something specific.
On our stations board, I had the pairs written up on cut-outs and squares of construction paper for each color. Two pairs of students were next to one color square each day and I just moved the construction paper squares down each day to a new pair of students. It worked really well because I could say, "Jane and Bonnie, go pick out a green station!" and they would go get a green tub. When it was time to rotate, they stayed in the same color station but swapped out tubs with the other pair who had the same color...so the green tubs switched, the red tubs switched, etc.
I did free centers differently...I let them pick their center and had a rule of four to a center. I tried to let different children pick first every day-sometimes I would do it by their classroom number; other days I did it by behavior; sometimes I did it by where they were sitting...I switched it up so everyone at some point had a turn to pick first. At the beginning of the year I pulled out the centers I wanted them to do and put them in the space I wanted them, limiting the total number of centers to five...by the end they could pull out any center they wanted since they knew where the stuff belonged and where that center went in the classroom.
I liked having a very structured approach towards literacy stations and rotating versus the more laidback free centers...it gave them a chance to do things differently for each activity.