Squats are great because they work EVERY muscle in the lower half of your body. They are expecially great when it comes to toning up those glutes and thighs. There are a few things to make sure of when you are doing squats.
1) Watch your form. It is very important that you do these right. You want to work your muscles correctly, and you want to avoid injuring your knees.
2) Use weight. Women are usually afraid to load on the weight because they think they will get bulky...yada yada yada...NOT TRUE. Impossible in fact. I once had a professor at BYU that said if you'd do 3 sets of 15 squats (with weight) 3 X a week you could go down a few pants sizes. I'm with him!
Start from a standing position feet hip width a part. You can hold dumbells in both hands by your sides, hold dumbbells on your shoulders, use a bar on your shoulders, or a smith machine.
I want you to think stick your buns out. Butt to the back wall! You want the lower half of your leg, from the knee down, to essentially stay in the same place as you squat down. Stick your butt out and back instead of having your knees go forward, slowly go down until you are in an airborne sitting position. You want your thighs and that magnificient Femur bone parallell with the floor at the bottom of your squat. If you don't go low enough you aren't working the full motion of your leg muscles. To get the best workout get low! All of your weight should be in your heels. You should be able to lift your toes back towards you. Also try to keep that chest up. For some it helps to look high with your eyes so you are less likely to hunch over. Slowly come back up and return to standing position, and There you have it. I would do three sets of 15 repetitions each time you lift weights. They are the miracle worker!
Tip: If you are having a hard time getting your form down grab a chair or bench and put it behind you. Squat down like you were to sit in the chair but barely let your glutes touch and come right back up. The chair should be far enoug behind you that it forces you to stick your hips back and have proper form.