This is where you have to be careful. There a lot of rogues out there who will seize upon your desire to be published and will try to rip you off. You can self-publish for next to nothing. Follow the link.
An excellent piece about writing horror by Stephen Volk, author of the BBC's Ghostwatch and the brilliant books Whitstable and Leytonstone.
Stephen King is one of the most prolific and successful writers in the world,. This is a talk he gave at a US university a few years back. With over 350 million books sold worldwide, he probably knows what he's talking about. There are few nuggets to be gleaned here. Well worth your time. (Warning: some of the language may not be to everybody's taste) And if you haven't done so already, read his book, Stephen King On Writing.