I don't do squats very often, but when I do, I usually do the variation where my heels are elevated, rather than the traditional back or front squat with a barbell. This allows me to really dig my heels into the ground and fire up my glutes. Think of it as extra booty activation. To do this move, I usually do a goblet squat with a kettlebell or dumbbell, and I use a pair of 10-pound weight plates underneath my heels. It's only a slight elevation, but it makes all the difference.
Personal trainer and "Glute Guy" Bret Contreras uses this method with his clients frequently, and it seems to be working wonders! Rather than doing normal reps, I like to pulse it out at the bottom of the squat. That gives me the chance to dig my heels into the weight plates and squeeze my booty. Give this a try and see how you like it!