First, as PP said, finish the book. Then get feedback, rewrite, and clean up. Most novels need lots of editing and rewriting before they're ready for publication, it's amazing how much longer the process can be than it looks at the outset. I have completed and sent out three novels so far, and have collected quite a stack of form rejections from agents. It can be quite a long process.
Getting good feedback isn't the easiest thing in the world, either, nor is knowing what to do with that feedback. I've gotten several friends to read my work over the years, and most of them don't have anything useful to say. Think about your friends, and which of them read a lot of books in your genre. They'll be a good place to start. Personally, it takes me a long time to process feedback, and it's usually a year or so before I have enough distance from a manuscript to make truly major changes. If you're less defensive as a writer, it won't take as much time, but you'll have to be careful not to get swept off-track by suggestions that may not lead where the novel ought to go.
I've read several books about the submission process, but the ones I refer to most often are Your Novel Proposal: From Creation to Contract
and Writers Market (or now, more often, writersmarket.com). The Jeff Herman guides are also popular.
I always thought that it would be different for me, that I would be able to write and revise my first novel in the space of a year, and get an agent, too, but it's been closer to eight years, now. Some people do sit down and write a publishable manuscript in the space of a month or two, but they are vanishingly rare.