Joe Allebaugh , Feb 04, 2010; 06:42 a.m.
I would use AI Servo for the AF tracking mode with orientation specific AF sensor points with point expansion. This combination on the 7D works well for me for sports action. Read over the AF section in the manual, and Canon has a site of video tutorials for the 7D - http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=3167. I also use the rear AF-ON button for focus and disable AF on the shutter release (under Custom Function setup).
Your 70-200 would be the lens to use, and better if it were the IS version. Set the ISO speed high enough to get speeds of 1/200 second or so to stop action.