For soccer I just do juggles and some runs. Play around a bit. Stretches.
For hockey, well.. hehe, I run up and down my stairs to get the blood flowing, and I eat pasta, and the most important thing, drink water, lots of water. Water helps to keep you hydrated so you won't get cramps and will last longer out there without getting tired. At the rink, I do runs with my team and then we stretch.