Then you need to think about what that means to you. Certainly one obvious rule I would consider may be around who orgasms first or even if they are allowed to orgasm at all. You may also want to look into chastity as well as teasing sessions (and here you have a built in reward/punishment cycle as permission to cum becomes a reward and forbidding it a punihsment). Things like how they look and behave could also be important - you want them to be sexually attractive to you so what do you consider sexy? This may involve them doing some form of exercise and diet programme to maintain a trim figure (plus, sex is always easier when you are fit and healthy) as well as maintaining a hiarstyle and mode of dress which you like.

Good luck!