Mistake Number 1: Rounding your back during the deadlift. Unless you are training as a powerlifter, you can risk injury utilising a rounded back as opposed to a neutral spine.
How to Fix It: Practice good form by maintain a neutral spine with a forward gaze.
Another way to fix is it by focussing on the hinge-movement. The hip-hinge is what drives the deadlift, so by making sure to extend your butt back and wait until you feel a stretch in your hamstrings and glutes to extend back into lock position.
Maintain this movement until you have finished your set by mentally focusing on the hip-hinge (controlled butt back, feeling the stretch in the glutes and hamstring then up into a straight lock position).
There is no need to hyperextend into the lock position, rather, you can try a one second glute squeeze at the top and keep the movement fluid.
Mistake Number 2: Allowing knees to cave in during squats and bridge-movements.
How To Fix It: I will give you an internal and external mental queue that can help remind you to keep your knees out.
External Queue: Externally rotate your knees outward. If it help you to practice good form, mentally draw your focus towards externally extending your knees towards the walls of the gym. This is a mental queue that utilizes an external focus and while external queues are primarily utilised for strength purposes, they may work well for you.
Internal Queue: For hypertrophy, you can are better off using internal queues. You can either use a resistance band to push your knees against or remind yourself mentally that “knees out” can better activate the glutes. Simply recite “knees out on the way up (/ down)” to yourself while you squat to remind yourself to do it.
Mistake Number 3: Driving through toes and not through your heels during either the squat, leg press and lunge if your goal is to grow glutes instead of quads.
How To Fix it: If your goal is to grow the gluteal muscles, then you need to activate them through pushing with your heels. This means redirecting your focus to your heel and actively pushing up through it them.