In our class (7 year olds thru adults, white thru brown belts) we usually take about 15 minutes to warm up. This includes- arm, leg, and neck streching, 50 jumping jacks, running in place, more leg streches, 50 crutches, leg raises, and 20-40 pushups. In that order. Starting from the jumping jacks, the highest rank usually leads. We also focus on breathing for a few minutes at the end of streching. Every once in a while we will pair up and stretch each other for about 30 minutes. Usually this involves one of us laying on the floor and the other pulling our leg back (one at a time) or a person standing against a wall and the partner pulling the leg up. Or we will both sit on the floor facing each other with our legs apart and grab each others hands. Then one will lean back and the other forward.