Well, the first thing to do would be to polish up your work until you couldn't make it any better, give it out to people to read and revise it again based on feedback.
After that, I suppose you'd just start querying agents. There's a specific way you have to write your query later. The most important part of which is, it should have NO typos or no weak links, not on the first read-through anyway, 'cause then the agent will just slush it.
There are many good websites/blogs that give you tips on how to write a query letter. This post is my favourite one, though it's old:
http://blog.nathanbransford. com/20...r-mad-lib.html
Here are a few more:
http://www.agentquery.com/writer_hq.aspx
http://queryshark.blogspot.c om/
Research the market. What do agents, or, for that matter, publishing houses look for? (Some do accept unsolicited manuscripts). There are competitions where you can submit your novel and land a publishing deal, and they don't cost a thing. Look out for those! (The biggest example being Amazon's Breakthrough Novel Award Contest, it happens every January).
And the best thing, of course, is to write, re-write, edit, re-write, cut, cut, cut. You want your novel to be the tightest and best it can be.
~this is all for the traditional publishing route. Can't help much with self-publishing, except for saying that it requires investment of money~
