The American Heart Association has lots of videos for brief CPR training. For those with a smart phone, look at your app source for a tool such as AHA's Hands-Only™ CPR to help you maintain the beat. Be sure to call 911 first! Then push hard and fast to help save a life.
Compressions per minute are vitally important to the success of CPR. Recent investigation has determined that too fast, more than 145 compressions per minute, means the push is not deep enough to be effective. It must be at least 5 cm (about 2 inches) to move the blood. Think of the Bee Gee's tune "Stayin' Alive" and that should help you maintain the best rate of closer to 100 compressions per minute without wearing out before EMS arrives.
The hospital offers in-depth CPR training for health professional according to AHA guidelines.
http://www.nlm.nih.gov/medlineplus/news/fullstory_127754.html Reuters Health story dated 7-30-2012
Monsieurs, Koenraad G. et al. Excessive chest compression rate is associated with insufficient compression depth in prehospital cardiac arrest. Resuscitation. Article in press, uncorrected proof published online July 23, 2012.