For me it just took practice to figure it out. This is hard to describe but I'll try - besides the "traditional" up and down movement I'll usually go up, tilt my hips back, go down, and tilt my hips forward. My boyfriend loves it when I do this and go real slow. Sometimes I'll learn forward and rest my head against his shoulder and grind against him that way or he'll thrust up into me. This is making me realize how much I love being on top.