Big advice on any type of lift:
I don't consider myself a master by any means, but this advice can add weight to any lift.
Man handle the bar, have some respect for the weight your moving, get pissed off.
When you squat, or do any other lift for that matter, but especially when you squat, you need to be TENSE. Your shoulder blades need to be fully retracted, your traps got to be tight because they are supporting the weight, not your shoulder and neck.
Don't come into a squat handling the bar all soft and tender. Shake the squat rack through the bar when your getting set up, build a solid foundation with your body under the bar. Before you unrack it take a huge breath and inhale straight into your chest cavity, then after you walk it out, take another deep breath before you go down for the rep, do this for every rep, exhale as you come up. TIGHT.
I don't want to toot my own horn, but watch this video of me as I prepare to squat. Notice how I literally charge under the bar and try to get the most tension as possible within my body before I even unrack the bar.
Back Squat: 450x1 - YouTube
Watch the goofy face I make right before I unrack the bar, you can see me taking a huge, deep breath, allowing me to tighten my core and provide maximum support. Also notice the depth, that is a competition squat and I went deeper than I had to. When you squat get solid depth, IMO below parallel, that is the depth that puts hair on your nads.