Soon after my novel "O Father" won the 3-Day Novel Contest in 1990 and was published the next year I began working on a sequel. I liked the characters and story and, apparently, the readers did, too.
Turned out publishers . . . not so much.
I tried my best to get it published but it just didn't happen. As I continued to pitch the manuscript I moved on to other books. The sequel, or the second book in a series, sat in a box in the attic for a long time.
Then along came the Internet, self-published e-books, and Kindles and Nooks.
These days I'm working on a new novel and, at the same time, editing and revising that sequel. I much prefer creating something new to editing something not-so-new. I mention all this because maybe you have a completed manuscript or one that partially done and 2012 is the year for you to dig it out, look at it objectively, and decide whether or not to publish it yourself or finish it and then publish it.
Whether you've just finished a new one or have a long-ago-completed one on hand, it's going to need another round of editing (and proofing) before you send it to a publisher or publish it yourself.
Finish editing the new. Finishing writing the old and then give it another edit. At that point let some people you trust (ones who will be honest with you and whose opinions you value) take a look at it. It could be it's not publishable but then again . . .