Favorite exercise

When it comes to leg exercises, most people first think of squats (there's an expression that "squats are king"), but I've personally come to appreciate the deadlift as a much better choice. It's been shown that putting the bar on the back of the shoulders (as is done with squats) puts the knees in a position to receive more stress than keeping the weight in the front of the body. Also, resting the bar on the shoulders can have a bad effect on your neck and upper spine over the years. I know because I had both knee problems and neck problems that seemed to come from excessive squatting. By switching to deadlifts, I don't have those problems anymore. Deadlifts just seem more natural anyway--I mean, when you're just doing things in real life and you need to lift something heavy, do you think you'd put it on your back or just pick it up?
The deadlift is, in my opinion, the most basic weight training exercise and it works your entire body in one exercise. You can do this with a barbell, with dumbbells (as shown in these pictures), cables, heavy objects, or even with no weight at all. However, this movement must be performed correctly with strict attention to keeping the spine in a safe position.
There are several different ways to do this exercise, but here's a good way to start. Start, as in figure A with your weights on the floor in front of you. First, stand straight, keep your core tight with your chest out and your butt slightly sticking out, feet a little wider than shoulder width. This keeps the muscles along your spine flexed throughout the movement and protects your lower back. Now squat down, maintaining the "butt out" position (NEVER round your back, as shown in the third photo). Keeping the weights close to your body, pick up the weights, grip tightly, keep your shoulders back and head up, and then stand up. When you're standing with the weights, keep everything tight. Then, keeping your back in that tightened position, squat back down almost to the floor, then stand up again. Do 2 or 3 sets of 10 to 15 repetitions, resting about a minute between sets. It's super important that you don't let your back round (this puts the muscles in your back in a vulnerable position). You can do this with your feet closer together or farther apart. Closer together will work more of your quadriceps, farther apart will work more butt and hamstring muscles.