The Thigh Squeeze
If you're on top, or he's entering you doggy style, it might seem like common sense to open your legs to allow him access. But once you've got a rhythm going squeeze your thighs together and pull your pelvic floor muscles 'up' as if you're trying to stop a pee mid flow. This will tighten your vaginal canal and increase the friction on your clitoris. A guaranteed orgasm inducer.