Squats are one of the most powerful exercises for transform your body. That great power means you can also seriously hurt yourself. It is one of those things worth going out of your way to make sure the conditions are optimal. If not, you are better off not doing them as the kind of injuries you get can last for years.
1. Have a professional trainer show you how to do squats in person
2. Have a professional trainer watch your form many times until you feel confident you got it down
3. Do squats in a squat rack
4. Do squats with a weight lifting belt on
5. Do squats with a spotter present
Number 4 is the only one I would question. Belts are useful as the weight gets heavy (70-100% OF 1RM) as they help to create create extra stability through the core region as well as helping generate intra-abdominal pressure.
For the regular gym goers that are squatting for reps I would be personally be advising NOT to use a belt so that they can learn to activate their core and secondary/stabilising muscles. For someone that's squatting a weight that's in a normal rep range, they'll get much more benefit from not wearing one. Just my 2c of course, but apart from my clients that are powerlifting I advise against using them ~ girls especially (you'll also find that people tend to become reliant on them very quickly); the results in developing greater core core activation/strength from squatting without a belt is fairly evident.