I've gotten good results from mixing power training and strict isolation work. For instance, if I'm working the biceps, I'll start with some heavy barbell curls, for maybe 3-4 sets @ maybe 10,8, 8, 6, then a couple sets of heavy cheat curls where I add a decent amount of weight to what I was just curling (strict) and bust out a few reps (usually 4-6). I make sure to cheat only enough to complete the rep. While I'm doing some cheating, I'm making my biceps work as hard as possible, past the point where they could move a weight with strict form. Then I'll do a strict exercise where I can really concentrate on my biceps contracting so that I get every single muscle fiber involved! So my biceps workout might look like this:
Barbell Curls (with an arm blaster) x 3 @ 10, 8, 8
Heavy Cheat Curls x 2 @ 4-6
Incline DB Curls x 3 @ 8-10
I might switch out incline DB curls for preacher curls one week, or maybe one arm concentration curls, cable curls, or some other biceps exercise. And sometimes I'll do three or four exercises with only one set per exercise, or maybe two exercises with two sets each. I like to keep my total number of sets for biceps 9 or less, but make those few sets be really intense. So I'm mixing heavy and light weights together. Also, I make sure to flex a lot between sets.