It depends on your intensity. I personally use two sets per exercise. I train a lot like Dorian Yates in a sense. On my first set I use a moderate to heavy weight to reach 8 to 10 reps. On my second set, its balls to the wall as I try to get 5 on my own, plus 2 forced, then a negative. It works good!!! There is no need for me to do a third set. Of course before you start your two sets, be sure to warm-up with a light weight to prepare the joints and to get the blood flowing. Lets say you are ready to perform bench presses and you warm up with two sets. Your next two sets will be your building sets. When you get to your incline movements, your chest is already warmed up, so there is no need to perform warmup sets for the incline. Just make your two incline sets as intense as possible. It also helps to have a training partner or a spotter when you practice this type of training.