Q: What is the best way to work my leg muscles, to gain muscle, using only free weights?

A: Free weights are actually the best way to build muscles in legs or anywhere else in your body. For the legs, the two best exercises are probably the squats and the lunges and there are several varieties of each.

You can see the standard barbell squat and the in-place dumbbell lunge on my Exercises page. In order to do the squat as shown there you must have what is called a 'squat rack' from where you'd pick up the barbell on to your upper back and onto which you'd put the barbell back after you're done.

There's a variation of the squat that can be done with dumbbells and does not require the rack. You simply hold two heavy dumbbells with your hands by your sides. For the lunges, there're variations too. Instead of using dumbbells you can use a barbell, holding it on your traps/upper back like shown in the barbell squat video. You can also do walking lunges instead of in-place lunges -- there instead of returning to your original position after each lunge, you'd be lunging forward as if you were walking with these huge exaggerated steps. You can do walking lunges with dumbbells or with the barbell as well.

One very important note about any of these leg exercises with free weights is that you have to be VERY CAREFUL when performing them and ALWAYS MAINTAIN PERFECT FORM as shown in the videos. Your back has to be perfectly straight, your knees have to be bending along the same plane as your toes point in, not inside of it or outside of it. It is a very good idea to get a trainer or at least somebody who's an experienced weightlifter and have them work with you using very light weights until you get the proper form down 100%. If you are not doing these exercises in good form, you can have a serious injury to your back or possibly knees. Always spend a week or two learning the exercise with very light weights before starting to push yourself with heavy weights.

As far as how many sets to do, I'd recommend anywhere between 4 and 15 leg sets total per week pushing yourself very hard with weights heavy enough that you can only do 12 reps or so of the exercise before needing a break. Do NOT go to muscular failure on freeweight leg exercises or you'll almost certainly injury yourself. But do push yourself hard.

Also remember that having a good diet is just as important as exercise when it comes to building muscle. Read my Nutrition article if you haven't already. Good luck!