Quoting Amber; ღ:" What type of 'rules'?"
Basically what you feel comfortable with your partner doing with the third party. Some women don't what their SO/DH to touch the other woman at all, he focuses all his attention on her and she get's to please the other girl. DH and I are very open, I let him do whatever he wants with the other girl, and if there's another guy he's cool with me doing whatever I want with him. It's all depends on what you and your SO are comfortable with. You just have to make sure all that is laid out before anything happens so there's no surprises/distractions when you're starting to get into it lol