This is the question John Warren asks in Chapter 2 of this book and if you're a Dominant, it's a very good question to ask yourself. This book is an excellent introduction to the 'kinky world' some of us live in from time to time.
While there are numerous other excellent SM books on the market, John's book covers topics not normally covered in other "introductory SM books, like how to act at a play party, and taking memorable pictures of your own private scenes. Also included are sections on First Aid, "Stalking the Wild Submissive," (very important!) and ways to do scenes that are exciting both for the Dominant and the submissive.
I felt the chapter that John's wife, Libby wrote (A Submissive Writes About Submission) gives an excellent insight for Dominants into what (at least for her) submission means and what it's about.
This book's second edition is now available on Greenery Press and it's an excellent addition to any kinkster's library, whether they are Dom, sub, or switch.