For the sake of a shorter article, I will only talk about the basics. Get a good powerlifting belt. A nice leather one will last forever if you treat it right. Whether you have a lever or a pronged buckle is up to you. I prefer the buckle. The belt will allow you to push air into your belly and drive into the belt. This will keep you tight. If haven't tried squatting this way-try it! It makes your mid section like an oak tree.
Shoes. Now, I know every great squatter out there talks about a certain shoe as being the best. Perhaps the best advice about squat shoes came from Louie Simmons: "Don't have $100 shoes and a 10-cent squat."
Of course, there are those people out there who make a living off of selling their brand of equipment. They will tell you that they sell the best squat shoe on the market. Unless you are handling 1000-pounds on a regular basis, I would not get concerned about spending $100 on a pair of shoes. You can spend that money on something else that will help your total far better then a pair of shoes! I find I like Chuck Taylors. They are cheap, and they last a long time. I also have a nice cheap pair of Nikes I got at a Finish Line. They have a flat sole and are a little stiffer then the Chucks. Experiment and find out what works for you.
I will say this. I used a pair of Safe SST Pro Series ($160) for my squat workout a few weeks back. The head coach had a pair, so I tried them. My hips and glutes did not get half the workout they get in the flat-soled shoes. Call me crazy, but a $30 pair of Chucks works just fine.