1. That life isn't binary. Sometimes she will have other things she needs to put first. Sometimes I have other things I need to put first. It may be health, it may be work, it may be family. It doesn't really matter which. What matters is that when we are in that position we expect (and receive) support and understanding not whinging or grumpiness.
2. That sometimes a scene won't work quite as planned. Shit happens. When something goes wrong, we'll stop, make it safe, work out why it didn't go as planned (if it's not screamingly obvious), learn from it and move on.
3. That communication is as important to me as it is to her. We understand each other pretty damn well, but neither of us are mind-readers.
4. That my #1 priority during any scene is her. Without her willing participation there is no scene.
5. That whilst I might be the one who appears to be in control, she has a non-negotiable right to opt-out at any time.
6. That if she ever has to safe-word, I consider it my fault that I've misjudged her reaction or misread the situation.
7. That the possessive pronoun "mine" works both ways.
8. That our relationship and how we interact with each other may be informed by observed experience, but it isn't defined by it. We'll pick up ideas, try some, discard others and keep those that work for us. We'll probably adapt them in the process because that's what we do.
9. That I'm always ridiculously proud of her. I stand taller when I'm with her, smile more broadly when I'm with her and feel privileged that she puts her trust and confidence in me. (Okay, I admit, this may on occasions lead to a teeny weeny bit of an exhibitionistic excess. Just sometimes.)
10. That the only reason I expect her to know these things without being told is because they are things we haven't just discussed in the past, they are things we live and breathe in our relationship.
(Note: Other flavours of D/s relationships are equally valid if they work for you and yours. If you feel inclined to give advice to others, then by all means tell them what works for you, just don't assume it should work for them, too.)