If in doubt on squats even after what jrahien has said try the following in front of a mirror, the most abused, but arguably most useful piece of kit in the gym for beginners.
Foot width at start is personal, but the most commonly recognised sensible is just over shoulder width.
Always lead with the hips, in other words they start the movement.
Keep yourself so you can see your chest straight on in the mirror, this will involve curving your back the way it should go, hyper extending not bending forward.
Knees follow feet in terms of angle, if this isn't happening move your feet to match the knees, it's safer and easier. Exception is if you are really going wide or knocking as Jrahien said, then sort your knees out.
Apart from the alignment don't worry about the knees, if the rest of your squat is right they cannot help but go where they need to be. Hips moving back and weight lowering will mean the knees bend naturally.
Depth is personal, the parallel is power-lifting minimum and therefore recognised as something you should aim for. Reality is this is where you will find most dispute. I agree that parallel should be your aim.
This is beginners tips and guidance only. It is a way to set you on the right path. As you progress in terms of weight and intensity you will fine tune to suit your individual physiology etc. to get the most out of it. You will also use variations like sumo, front, jump squats, high an low bar etc. If I started trying to type you through all of these I would be wasting a lot of your time, and confusing you because each is slightly different. This is just the generic simple squat.
Jrahien will have far more qualifications than me and there are very rarely times when my experience trumps his knowledge, this like most cases isn't one of them. I cite 23 years of training, progressing from squatting with a 30kg bar to 195kg under the watchful eye of 3 power-lifting judges, if they say I squatted well you can trust I did, they are gits who let you get away with nothing.
I have trained people of various abilities to be able to do squats of various types, including one person with no arms, if you are really good on form you can squat without holding the bar safely, but if you have no arms have a competent spotter. Latest person I have trained into them is my early pubescent son he is currently lifting a piece of plastic plumbing pipe with 5kg on it with perfect form, high and low bar.
It is a good thing that you are wanting this to be perfect. This is one exercise that can be very dangerous if done badly.