With the squat there are several different 'ways' to squat. I always squatted with my feet splayed a little at a little wider than shoulder width and got my 'ass to the grass'.
Rest the bar where it feels comfortable. For a regular squat, the bar shoulder rest on your traps, front squat it should run across your anterior delts and upper chest. As for the grip, I just hold the bar about a foot from each ear. When squatting, try and keep your back upright. I suggest squatting first with just the bar, getting the feel for the movement and nailing the form. Slowly add weight. Form is more important than weight at the start. In fact, form is always more important than weight