Here's a video from a homey at Pittsburgh Boot Camp that does a goodjob talking about the best form for the lunge. If you don't know the joy of this movement. Be prepared. It hurts so good.
That's a movement that works both the front and the back of the leg at once. Nice. Efficient. Hot.
After a five minute warmup on the treadmill, I hit the weight room intending to increase the resistance and the intensity. I added 10 lbs. to each exercise and reduced the rest period between. I want a simple, serious workout. A fast workout - one that wrings me out when I'm finished. The purpose here is two-fold. First, I want to build muscle mass as quickly as I can. That comes from lifting heavy weights - as heavy as you can safely handle. Second, I want to build as much cardio work into my weight training as I can - the way to do that is to keep moving, just like on the treadmill.