If you are doing 245 with bad/improper form you really need to back off and get the form down right. This is extremely important for further progress.
The type of squat you are doing is going to dictate the amount of depth, back angle, knee extension, knee angle, etc...
There are two main types of back squats, high bar and low bar. High bar squats, or olympic squats are performed by placing the bar high on the back on the trapezius. To get a good view of where to place the bar, which is important, retract the shoulder blades back very far without a shirt to see the shelf that the traps create.
What I do to retract the shoulders is place my hands on the bar first and press myself through and infront of the bar and then slowly back up until the bar is right above my traps. I keep my elbows back and up, not down perpendicular to the ground which I see so many people doing. This "locks" the bar in place a bit and allows the wrists to remain straight and not under stress.
The more flexible you are the more narrow you can stand. Generally, you want to stand with feet right at shouder width apart 12-15". The farther out you spread your legs the farther out you will foot angle will change. A good way to find correct foot angle is to sit in a chair with feet together pointing straight out. Start moving your thighs apart and notice the angle that your feet naturally take. When they are shoulder width apart, this will be the angle that will probably be right.
When you descend you want to keep your head straight or just down a bit. Break first at the hips and sit straight down. Do not let your knees travel far, a good rule is to keep the knees right above the toes but not much further. Your knees should also be angled out so that they trace directly over the feet and do not cave in or push out too wide. Caving in seems to be a common problem, especially for noobs who have trouble with flexibility. You want to keep your back as straight as possible. Depending on your individual anthropomorphology, the angle of your back will be different but you should be fairly close to being upright.
Another important point is to keep the weight on your heels at all times. Descend in a controlled fashion, while holding your breath. This is important as the air in your abdomen will keep you stable throughout the movement. Do not breath in or out during the rep, only after its completed. This is called the valsalva movement.
Squat down past parallel until your thighs and calves connect. If you are not flexible enough to do this I would suggest a lot of time sitting deep in the squat position. The bottom of the squat is important to use the stretch reflex mechanism that occurs as your muscles are stretching out at the bottom and bounce out of the hole. It is not violent like a slinky but controlled and natural.
Push through the heels hard at the bottom and come through hard agan with your hips at the top.
Here's a really good video of an olympic squatter. His knees cave in because of the weight but otherwise his form is excellent and you can clearly see his massive shelf of traps that holds the bar.
http://www.youtube.com/watch?v=3Y8yKSJbpFI&feature=relatedLow bar squats can be seen described in the stsarting strength wiki I linked early. You can lift more weight with low bar and there is a lot of debate which one is better but high bar seems more natural with less tress on the sholders and what olympic lifters do so thats what I do. I would do lots of squats with just the bar every day for a while to get the form down just right.