HOW: Start on your back with one knee bent on the floor, with the opposite leg perform a straight leg raise. Next, drive your heel into the ground and lift your hip up towards the ceiling with the bent knee. At the end position your knee, hip, and shoulder should be in one straight line. Hold the end position and squeeze the glutes, then slowly return to starting position and lower the straight leg back down.
FEEL: You should feel your glutes work to control this motion. At no point should you feel your low back muscles doing the lifting motion. If you feel it only in your hamstrings, try bending your knees a bit more and repeat. The straight leg will be working the front of the hip and thigh muscles.
COMPENSATION: Avoid arching at the low back as you perform this. Don't let the knee bend with the leg that is elevated.