This is how I first determine my groupings for the year and get to know my students a little better.
I have them fill out this information sheet, as I like to read their perceptions on math (or whatever subject you teach) and what they are interested in. I will use their interests to form better lesson examples, include them in word problems, etc.
Then, they are to choose an answer for the 4 study habit questions. At the end of the time, they introduce themselves to others in the class and find someone with a "different" study habit in the "different" box. They sign each others papers, and then go off to find a pair who has at least one member the "same" as the other box. Basically, I am trying to form study groups that have similarities and differences so that they can work with someone who isn't just like them, but also not too different that they would not enjoy studying together.
You can always make this your own, or skip the "same and different" part of it.