Some people say that in a threesome, two people want to hook up a lot more than the third does. How do you make sure that third person doesn't feel left out?

Ian Kerner: Everyone needs to be on the same page in terms of what is going to happen, including whether the focus is more centered on two people or on all three people.

While laying ground rules might seem to kill the spontaneity, most people will feel more comfortable when they know their preferences will be respected.