Try to get jobs freelancing with d20 companies to start with. The en-world forums are a great place to look for work (http://www.enworld.org/forumdisplay.php?f=68
) and RPGnet can be good but it's mostly art related (http://forum.rpg.net/forumdisplay.php?f=12
) but also google search and watch the forums on company websites. There may be other good places to look - if you find one, by all means write me about.
Getting someone to publish your work is difficult. Each d20 publisher is pretty much self-made and they have their own ideas they have worked very hard to get going. They may or may not like a submitted product. Even if they do, it'll have to be edited, chances are the format will have to be reworked. Art has to be paid for plus e-publishing or printing costs which can be pretty stiff. It's a major investment, especially for smaller companies which can make it or break it on a single product.
I have written four books that have not been published, one because the company I wrote it for vanished. Over the last three years I have submitted them a number of times but I have been turned down each time. At first there were virtually no responces. Once I published a few magazine articles and got my first book out and got my webpage set up - people started replying.
Things are clearly getting better but my dreams of getting my books published have been put on hold while I freelance which has been a great experience. Publishers tend to give freelancers almost total freedom in terms of what they write. They are more concerned with format. You get almost as much freedom as working on your own and the book is probably going to get published. I figure that once I get enough publishing credits, bang on enough doors and get noticed enough, I will reach a position where people will publish my work, or I'll go crazy and become a publisher.
The difficulties in getting someone else to publish what you have written is what makes people start their own companies. Just about every company out there has a campaign setting designed by the founder that he or she wanted to see published.
Smaller work is much more likely to get accepted. I have published a number of magazine articles. It is my longer books, 30 000 words or more, that are difficult to get published. First, a publisher is only going to look at 10 pages, or so, from the book. It's frustrating trying to explain to a publisher how positively amazing your material is, from that but you make do. Someone buying the product is going to have less information than that before they pick it up.
Don't give up. When I started into freelance, I wrote 75 companies asking for work and only 5 responded. The first told me not to write them such letters! The other four offered me work which was fantastic.
One of the problems is that the d20 market is flooded. If you can imagine it, it has probably been done, twice. It's a good idea to start learning non-d20 systems and expand what you can do. I'm looking at Battletech and I want to be a novel writer. This way you will be better ready when a job offer comes along.
When 4th edition comes along there will be many new opportunities for work, so hang onto anything that hasn't been published and get ready to update it! 4th edition scares the heck out of me. I wonder how the RPG market can handle all this massive flooding of books - however, book shelves have always been full of books. There will always be a call for new books.
Well there is my advice all mixed up in that.