The lunge is a little more complex than the squat, but equally effective, and if you want buns of steel, this is your exercise.
1) Stand with your feet shoulder width apart and take a long stride forward, keeping the same width between your feet.
2) Raise your back heel off the ground and drop your back knee directly down to a point just off the ground. Your front shin should finish vertical, knee over your ankle. Keep your vision forward and the majority of your weight through your front heel.
3) When lunging, keep your torso upright and don’t stop at the top of the movement. Feel this in your glutes and quads and you’ll know it’s working.