A good leg day should be full of hinging. This hinge movement allows you to use your glutes and hamstrings without putting impact on your knees. There are several variations of this movement based on your experience level but I find this to be the most applicable at any level.
This movement can be done flat on the floor, as well as with your feet elevated. Begin this movement with your back flat on the floor and your hands beside you. Then squeeze your glutes to lift your hips of the ground. End the motion when you feel the hardest glute contraction or when your hips are in line with your legs and core. Also, try the single leg variation for a challenge and extra hamstring work.
Hip hinging is the most crucial part of leg work. Working through this range of motion is an ideal way to get the most mobility, strength, and stability out of your legs. Make sure you practice this move when you are warmed up to avoid any tightness or injury.
The goal of this movement is simple, the setup is complex. To start, roll your shoulders down and back, locking your lats in place. Put you feet about hip distance apart and a micro-bend in your knees. Slowly lower down keeping the weight close to your shins, keeping your spine straight. Stretch your glutes and hamstrings back without bending your knees further. When you feel the deepest stretch, squeeze your glutes to return to standing.