I've really struggled to make effective cooperative groups for projects. I like trying to let kids who are friends work together because they are more willing to work with their friends than with people they don't like. Unfortunately, in the middle grades, friendships change daily.
I invented this little form to help me sort out who works well with who and who is not on speaking terms with who. The best part is that they have some buy-in into their groups, but I have the final say of who gets to work together. This helps in the situation where kids are friends, but one knows that the other just mooches a good grade off of their hard work in cooperative projects. I always collect these myself and promise not to show their forms to their peers. Occasionally I keep a couple in a file for parent-teacher conferences or special education case workers.
Each sheet has two copies of the form. It is intended to save paper. Just photocopy for half the number of students you have and use a paper cutter to cut them into half sheets.