Are you training for bodybuilding purposes or for powerlifting purposes? Knowing the answer will make a world of difference in how you squat. Or at least it ought to.
Here are the foundational differences between squatting for powerlifting purposes (increasing your 1 RMa) and squatting for bodybuilding purposes (increasing muscle mass).
Reps. Mix lower reps and higher reps for hypertrophy (8-12 and even sets of 25 or 50) and use lower reps for strength (1-5).
Weight. Always aim to get stronger, but for hypertrophy you can build muscle with heavy weights and with lighter weights. For strength, always train pretty heavy.
Tempo. Know how to use tempo to your advantage to build muscle and strength. Tempos with a slow eccentric (negative) are often useful for bodybuilding but usually have no place in powerlifting.
Time Under Tension. A longer time under tension is great for hypertrophy but not so great for strength.
Bar Placement. Generally speaking, use a high-bar placement for bodybuilding squats and a low-bar placement for strength work.
Body Position. Keep an upright body posture when trying to build muscle. (If you're a taller lifter, you may have a tendency to lean forward when lifting heavy weights, but that's fine.) Body position doesn't matter so much for powerlifting. Use whatever works for you.
Rest Time. For building muscle, mix up short rest periods and long rest. When training for strength, have a minimum of three minutes rest between sets to maximize recovery and strength.
Range of Motion. The simple rule of thumb for both disciplines is squat as deep as possible without pain or discomfort. Work on mobility if needed to improve range of motion.
Stance. Generally, a bodybuilding squat requires a closer narrow stance, while a powerlifting squat does better with a more hip dominant stance. However, your squat stance is based very much on the genetic construction of your hips, so find a stance that feels comfortable for you.
Muscle Contraction. When trying to build muscle be sure to focus on squeezing and contracting the muscle as hard as possible. Your rest time at the top is a good time to squeeze. Forget about squeezing the muscles for powerlifting. Keep tight, but use this time to recover slightly so you can be strong for your next rep(s).