http://www.asmi.org/SportsMed/throwing/thrower10.html
These are the ones I do.
The 'band' that the guy uses can be picked up at the local Walmart, or any other 'fitness' store.
Also, look up dynamic stretching.....and do it prior to every 'game'....or throwing session. And after the game, do some static stretching.
Don't reverse that process though; if you static stretch a 'cold' muscle you put it at a bigger risk to get injured.
Oh, and the arm circles thing works awesome.