This is going to sound kind of cheesy, but I work with alot of Meta physical lifting. Get a basic understanding of how each muscle works, then invision the way the muscle works during the exercise. Think about the muscle elongating and filling up with blood, and then contracting all the energy out as the fibers over lap (I realize this isn't how a muscle specifically works, but it helps while you're trying to invision it). It really helps to have a partner or trainer who understands this and can talk you through it to remind you of it as you are doing a set. Metaphors will help to keep your attention into the muscle, which is ultimately what you are trying to do.
Using this technique will make it much harder to lift heavy weights. It's quite extrordinary how quickly you will fatigue with lighter weights.
