Other than being safe and respectful of yourself and others, there are no rules. There are lots of opinions, ideas, theories, etc., many of which I find valuable, but how you dominate and build your relationship is entirely up to you. Do what feels right for you and your partner(s). That being said, I rarely miss the opportunity to blather on about my opinions....
Domination is not about you servicing the sub, running the sub's life or taking responsibility for the whole relationship. D/s is a relationship between (hopefully) two responsible adults. I've come across a number of people who identify as submissives who think submission means an abdication of personal responsibility. Don't have anything to do with them. And don't let anyone tell you everything is your problem, fault, job, whatever, because you are the domme (same for subs).
Make sure whomever you play with is mentally fit. Don't make yourself your sub's therapist or take it upon yourself to help them "work through issues". Even if you have training in the mental health field, this would surely violate ethical standards. If someone has mental health issues, as many of us do from time to time (no stigma) they should speak to a professional.
Make sure you know what you're doing technically. If you want to get in to needle play, flogging, bondage, whatever, do some research, go to demos if you can, read books, watch some of the fine youtube videos out there and go slowly. Even something as simple as binding a wrist can cause serious damage if not done correctly. Don't underestimate your ability to inflict harm.
Speaking of harm, know the difference between hurt vs. harm. Hurt for masochists and sadists can be exciting and gratifying. Doing harm is another matter. I like how this article outlines the difference:
http://www.asubmissivesjourney.com/BDSM_hurt_harm.html
Pick a partner you trust with whom you can speak to frankly. Foster a D/s relationship in which both you and your submissive feel comfortable talking about everything you do together. Your submissive SHOULD NOT feel afraid to talk to you or say how they feel. Take time to develop the communication dynamic before you get in to any serious play. Not only this will help protect you both, it will increase the intensity and pleasure of your play.
Educate yourself about how adrenaline and endorphins can influence the responses of both you and your submissive. In the midst of thrilling play your adrenaline can suppress pain receptors and your submissive might give you the okay to go much farther than you should. As you learn your submissive you'll learn how to better read how they respond. Also don't underestimate how heady you can get when playing. The temptation to go too far exists for the dominant as well. Another reason to go slowly.
I'll stop there. Hopefully others will share their thoughts. Let us know how it goes and share your opinions too please