Most intimacy guides stress the importance of better techniques, new positions and sex toys, all things that make sex feel better. That's fantastic, but it's only half the equation. Couples should also focus on stimulating the largest sex organ -- the brain. Sex is at its best when partners are both mentally and physically turned on. In my latest book, 50 Ways to Play: BDSM for Nice People, I combine the mental eroticism of the 50 Shades of Grey variety with kinky "how to" sex tips that can help mainstream couples turn their fantasies into real bedroom play.