This one isn't so much a marketing tip on its own, but a way to find more new tips and tricks. The nice thing about social media is that you can easily see what everyone else is doing. And if you're following the right people you won't even need to go looking.
I suggest following your favorite authors, both big names and those that might be less known. Mix it up between those signed with the big 6, mid-sized or indie presses, and those who are going the self-publishing route.
Pay attention to their online activity in the month leading up to their next release. Where do they go, who do they talk to, what contests do they run, what are their prizes, do they have a tour, what blogs are participating. Be sure to following them across all the available social media sites so you can get a good idea of ways they are promoting in different places. Take notes.
When it comes to marketing, you don't have to invent the wheel. Keep in mind that the tactics everyone is using are probably common because they work. While you should always keep your own audience in mind, there's no reason you can't duplicate some of the efforts of other authors. Just keep in mind that duplicate efforts won't always equate to duplicate results.