Just write. I'm amazed by how many people "want to write" or "have a million ideas" or have that best-seller simmering in the back of the brain, but never set the words down on paper. There's no mystery. If you want to be in better shape, eat right and exercise. If you want to be a better tennis player, get out there and practice. You're an aspiring writer? Start typing. It's that easy and that hard. All the rest (book promotion, establishing an online presence, finding a killer agent) may be important, but secondary.