Check out the sites and make sure that when you do them you keep your weight on your heels, stick your butt out big time while keeping your back straight not arched, and don't let your knees go past your toes when you squat. That strains the knees. Once you get doing them, add dumbbell weights (even soup cans will do). If you are lucky enough to be at a gym, use the Smith machine or barbell for a better squat, just do it carefully and stick that butt out.
If you want tips or modifications on strength training moves like this, check out the strength training thread in Exercise. There are a number of ladies who lift weights and they are a wealth of information.
