As we become more experienced in training, things like these become more and more important.
To become good at performing exercises and be able to lift food numbers safely, you need to become a MASTER of the basics.. and this means paying attention to each step of the movement.
The difference between a newbie squatter and an experienced one can be noticed as soon as the person approaches the bar, and these 3 steps can seriously make or break your squats, in case you're not doing them.
1️⃣ Upper back tightness: as you approach the bar, it's very important to create a strong shelf for the bar to rest on. You need to pack your muscles together as you approach the bar by picking the right grip width (that allows to create the most tension) and 'tucking your elbows in'. Don't over do it: you don't want your ebows excessively flaring out (unless you're Low Bar squatting in which case will be inevitable), but you still want to create a strong upper back tension.
2️⃣ Diaphragmatic breathing/Valsalva maneuvre: breathing when squatting is very important as well, because this tip alone could help prevent you from feeling "lower back discomfort" by stabilizing your mid section and creating internal pressure that creates stability for your mid section. Yes, you hold the breath as you perform the rep and you exhale at the top, once the rep is complete.
3️⃣ create lower body tension by screwing your feet to the floor: Too many people 'squeeze their glutes' by rounding their back and starting the descent with a flexed spine already.. that's not the most optimal way to do it because first of all you're not achieving what you're trying to achieve: You want to squeeze them by externally rotating your hips, kind of wanting to squeeze them "around" your spine. And you can achieve that easily by looking at your feet and allowing them to literally be screwed to the ground.