You can allow the teams to develop naturally but this can lead to friends picking each other and while in some cases this may be good in other instances they leave out others and can be easily distracted by their other interests. If there is a good balance of skills this may be good, but it is useful to try to ensure that the abilities are balanced so that the job can be done.
Give everybody a raffle ticket and put the stubs into a drum or hat. Make sure you mix them well. You pick the groups by pulling out the tickets. This is an excellent way to mix abilities and interests and gets past the “I don’t know anybody” or even the “I want to be with ……”. It may take a little work on them getting to know each other but this may be a good exercise to ensure they each do their own strengths and weaknesses exercise which can lead they to being able to assign roles and responsibilities more evenly.
Rank each person by some criteria such as another class they do such as art or home economics and each team then has a mix of interests. This does not however get past the difficulties they may have getting to know each other.