What's the best way to isolate my gluteal muscles when doing squats and lunges?

For squats, I recommend using what I call the "toilet" position. Squat like you would to avoid touching the seat, with your rear end leading the motion, not your thighs. Your feet should be parallel and facing forward, and your knees should not extend past your toes. To avoid leaning forward, which will strain your back, focus on something that keeps you looking upward at a 45-degree angle. Experienced lifters may want to try 45-degree squats. Stand with your feet shoulder-width apart, toes pointed out about 45 degrees (envision a wide V shape), then squat. This is an excellent exercise for abductors and adductors as well. For lunges: When you step forward into a lunge, lower slowly until your rear knee touches the floor. Hold for a count of two, then slowly rise up. Be careful: Pausing at the low point makes for a more intense contraction when you stand back up. Start out with much less weight than you generally use.