Squats are a great exercise--unless you're doing them wrong. Here are the top five mistakes and why you should avoid them.
1) ROUNDING THE BACK
It compresses the spine and can cause back problems
2) LIFTING THE HEELS
It puts a lot of pressure on the quads and ACL
3) FEET TOO CLOSE TOGETHER
This is also bad for the ACL and can compromise your balance
4) BALANCE ISSUES
Look straight ahead so you don't fall over
5) KNEES CAVING IN
This is terrible for knees, hips and ankles
Finally, wear the right shoes! Running shoes are terrible for this exercise, so pick up a pair of cross trainers instead.