Warming up for compound exercises, such as benching, deadlifts, and squats, is also important. To warm up, use weight that you can easily do for 15-20 reps for your first set. After you finish this set, work your way up in weight until you comfortably reach your working set. Try not to tire yourself out by warming up too much though. There is a balance to be found. Warming up will help prevent injuries.