Congratulations, you're published.
Social media is a great tool, but you're going to need more than a Facebook page and Twitter account to meet new readers.
However, you can't ignore the reach of social media, there are rules though.
You don't want to the that author who friends people on Facebook and then post links to your book on their pages without getting to know if they're receptive to it. This is why you have your own page. There you can and should post links about your book, reviews about your book, teasers from your book and the like. Do not, and I can't stress this enough, go to other people's pages and do this without permission. It make you look like a jerk and it turns people off. That's the last thing you want.
Twitter is different, but not by much. No one wants to follow you if you only talk about yourself. The 140 character micro-blogging site is as random as it gets. People want to get to know your work and you. Remember that. But don't be too randy. If you wouldn't say it to someone's face, you probably shouldn't tweet it.
Despite what you may have heard, people still read newspapers. Trust me, I know! I work for one. It's a good idea to get to know the editors and reporters at your local paper. Find out who covers arts and entertainment, that usually encompasses books. A crisp press release and copy of your novel sent to the right person could mean an article. Be sure to have a hook -- is your novel related to something going on in your city? Does your novel tackle some current event that the paper has been covering? Make sure you play that up.
Don't forget the library! Get to know the librarians in your local city. Libraries often host writing workshops and reach out to local writers. Sometimes you get paid and sometimes you don't, but you're always able to introduce your work to new readers.
The big question I get asked a lot is -- should I get a publicist? That's a personal decision, but if you decide to invest in a publicist, you need to make sure that he or she has the proper contacts to help you. We are still in a recession and paying for someone to promote your work should yield results. Avoid publicists who can't give you a list of clients they've help. Avoid publicists who can't write a proper press release or don't have local, regional and national press contacts. Also, avoid publicists who have lack luster reputations with the media and local people who have been to there events. It's your brand and you have to protect it at all costs.
Word of mouth is still key. People talk about great books. Make sure you get to know book clubs. Book clubs are the best way to get the word out about your book and, in my experience, they are filled with great people.
These are just a few guidelines. Trial and error will help you craft your marketing plan. Good luck.