By eliminating valgus knee collapse (inward collapse of the knees), you'll immediately improve activation and function of the glutes. When the knees and feet collapse or rotate inwards, the glutes and hips lose significant contractile capabilities. To avoid this, think about screwing your feet into the floor and pushing your knees outward so that the ankles and knees are stacked.
Also think about spreading the floor with your feet during lower body exercises. Besides increasing activation to the larger gluteus maximus muscles, resisting adduction also enhances recruitment of the smaller hip muscles. A simple exercise to quickly address valgus knee collapse is the plate squat.
Using a stance slightly wider than shoulder width, take one or more 45-pound plates (stacked on top of each other) and place the load between your legs and squat. In order to comfortably fit the plates between your legs, you'll have no choice but to spread your knees. This is a great prep drill to perform before heavy squats as a means of grooving an efficient squat pattern into your central nervous system.