Our eighth suggestion borrowed from the Penners is to aim for mutual satisfaction in each sexual encounter.
Mutual satisfaction is defined differently for different couples and differently for each couple at different times.
One thing it certainly means is that a person never forces his or her partner to engage in a sexual act against his or her will. I have seen men turn demanding when their wives don't desire to engage in oral sex. Oral sex is fun for lots of couples but if a woman doesn't want to do it, for whatever reason, then she shouldn't be guilted or coerced into it.
That isn't to say that there should be no fun and experimentation in sex. There should. A healthy sense of adventure is essential in relationship. Variety is important in sexual connection. Have some sex when you wake up, maybe sometimes arrange to meet for a nooner, some afternoon delight, sometimes around supper time, a quickie at night, and of course, take a couple hours and leisurely enjoy one another. Not all in the same day mind you. ;)
If a couple only has sex in the morning it will become routine and lose a sense of being a special part of the relationship. Likewise, during child rearing years, if a couple only waits for long blocks of time alone, their marriage could be sexless for quite a while.
So, have some courage and ask your spouse how he or she feels about your sex life together. Be willing to share your desires without them being demands. Be willing to move towards his or her desires as well.