Yes, I said it: daily routine. As an author you should be doing something every day to promote your book(s). I'm not saying you have to spend eight hours per day promoting your work. Most authors simply don't have time for that. But how about an hour per day? Yes, one hour. Send some emails, tweet away, interact on Facebook, participate on Goodreads and forums--you know, all that good stuff.
What's that you say, you don't even have one hour to spare? It's time to prioritize! There has got to be something you can remove from your schedule to make room for an hour of book promotion. Take a moment and write down your schedule and take a long, hard look at it. See anything there that doesn't need to be?
You and I both know that you'll eventually miss a day (I know I certainly have), but that's okay. Just move on. There's always tomorrow. Tomorrow becomes today--and that just happens to be right now. So what are you going to do (or what have you done) to promote your book(s) today? Seriously, tell me...
P.S. Of course, all of this is in addition to writing daily!