extend both arms straight in front of you, one over the other and place palms together with the wrists crossed, your right palm should be facing right and your left should be facing left. Interlock fingers and draw arms down so that they fold in toward your body and up under your chin. Then you can bring them back down and repeat the whole move again. (I hope I'm making sense its hard to explain).
Doing anything that gets both sides of your body (and therefore your brain) working together is good - raising your left leg and right arm at the same time and vice versa.
Also, if you count to ten or do some simple math in your mind, then hum a bar of any tune, or a scale, then count again, this also gets both sides of the brain communicating.