Safe sex is madatory, the only major rules my partner and I have are related to that. For example let each other know if something like the condom breaks and take a shower if you are going from being with one partner to the next (I have a bit of a weak immune system). Other than that we each try to have one thing that is "special" to each of us for the moment, though we are going to try to relax this as we gain more experience. For example, at the moment there are no overnight dates for either of us and we are to check in when we get home.
But I agree with the other posts, there are no permanent rules and the ones that are agreed on at the beginning of a relationship are often relaxed as things progress and comfort levels increase.