From my experience, doing squats is great for increasing the strength in your quads and hamstrings and also your knees. It is also a great exercise if you are looking to build some mass. The important thing to know about squats is they can be dangerous and harmful to your body WHEN YOU DO THEM WRONG. They are easy to do wrong if you haven't done them before but most exercises are. Another important point about squats is they are one of the best exercises you can do to improve your body when done correctly.
When I first started doing squats I didn't know what I was doing so I started off fine but I increased the weight too fast and my form suffered. I kept increasing the weight did not go low enough in the squat to compensate for too much weight. I also had poor flexibility in my hips and ankles. In order to properly squat the weight I needed to go down at least low enough that the tops of my thighs were parallel to the floor. As a result of not squatting properly, my knees began to ache. This ache was increasingly noticeable walking up and down stairs.
After this I decided to stop squatting, at least for a while which I now wish I hadn't have done. It would have been more beneficial for me to start over with light weight and make sure I had proper form. I did eventually do that but it was almost a year later. My knees still felt weak so I took it easy at first just using the bar and I didn't have any problems. I slowly increased the weight by 5 pounds each squatting session. I was following a 5 by 5 program where i was squatting 3 times a week. I then began working out with a friend of mine who had been squatting a lot longer than me so he was able to squat quite a bit more than me. This prompted me to start squatting more weight to make the switching of weight when he would do his set easier. I realized that I was able to squat quite a bit more weight with proper form than I was used to working with. After squatting regularly for a few months my legs grew stronger and I was putting on more muscle and gaining weight. My knees also felt stronger than they ever had.
From this I learned just how important it is to use proper form while squatting. It is not like most other exercises due to the fact that a lot more muscles and weight are being used. Another thing I learned was that you can't blame an exercise for your injury if you didn't do it correctly. After all, exercises are meant to improve your body not make it worse. Another thing I learned from my squatting experience was that you're stronger than you think you are it's just a matter of breaking through that mental barrier and also having the motivation to see what you can do.
I incorporate both back squats and front squats when I workout. I find back squats are better for building more strength and mass. This is because the bar is on your back and you have a much wider grip on the bar than for front squats. This means you have better control of the bar and can handle more weight. Front squats are better for improving posture and strength in the upper back. They also put more emphasis on the quads than hamstrings as you can't bend down as far because the weight is in front of your body. Front squats can also improve flexibility in the elbows and wrists depending on how you choose to do them.
When I do back squats, I place my hands on the grips on each end of the bar. To make sure the bar is even, I place my pinky finger at the end of each grip with the rest of my hand on the grip. I then begin to dive under the bar, putting my left foot out first then bringing my right foot parallel with my left. I place the bar on the top of my shoulder blades. Then I take a few steps back, placing my feet about shoulder width apart and firmly on the ground.I then stick my butt, out behind me and bend at my knees at 90 degree angle, the same way I would do so when sitting down. This is important to remember when squatting. I keep my upper body straight so that my back is strong and flat. (Note: When bending, your knees will naturally come over you feet. Also, bend your hips when sticking your butt out.)
When I do front squats I do them with my elbows bent back towards my body and the bar resting on the palm side of my fingers. I first set up by placing my fingers on the bar where I want them to be when I move my elbows up under the bar. I then bring my elbows up so they are under the bar and pointing at the wall so my upper arm is parallel to the floor. At the same time I move my feet under the bar to unrack it. This is all done while keeping my fingers at the same spot on the bar. I keep the bar and most of the weight resting on the front of my shoulders with my fingers just outside of shoulder width to help stabilize the bar. I then sit down and back into the squat the same way as with a back squat only keeping my center of balance closer to the front where the weight is. This means by knees will be farther over my feet and my upper body will be closer to an upright position. I try to keep my elbows parallel with the floor the whole time to ensure the bar stays resting on the shoulders.
From the results I have gotten from doing squats I would recommend trying them, both front and back squats, to anyone looking to improve any area of their fitness. If you have never done squats before, I suggest giving them a try. I would also strongly recommend doing them with another person, specifically someone who knows how to do them properly. This is important because they can watch you do your squats and help you do them properly.