This is a strategy to quickly create random groups.
Whenever you need to create quick groups for students/teachers to share their thoughts, ideas, what they've created, etc. have a set of multicolored index cards (four or five different colors depending on the number of groups you desire).
As students/teachers walk through the door, hand each person a different colored card or have the card sitting on a desk. When you are ready for them to get into groups have them partner up by using the index cards. For example, start groups out by having them find two other people with the same color card or find three people with different color cards. Continue using different card combinations every time you want the groups to change.