J.K. Rowling said on her site that the best place to start off trying to get published is finding an agent. Agents sell your books to the publishing houses. You can submit directly to a publisher, but you might not get the best deal.
I'm really liking the "Writer's Market" website (link is found in the "Links To Informative Sites" bar on the side). They provide you with a lot of information. I was able to do a search for a literary agent who works with the genre my story is in (young adult/fantasy). So far I was able to find 19 agents that I can submit my story to.
Most want a query letter along with SASE (self-addressed stamped envelope), some also want credentials, and others want at least 50 pages of your work. Some agents want you to send queries through email, others want you to do it through snail mail. One thing to note, see if they'll look at "new" authors. Some said they wouldn't consider an author's work unless they were referred by another writer. It was also warned that if the agent asks for a fee before they'll work with you, don't use them. They make their money when you do. Most want 15% commission for domestic, 20% for international.
If I find out anything else, I'll keep everyone updated! ;)