A quick recommendation for a useful guide for writer's in the 21st Century: Booklife, by Jeff Vandermeer.

What I have found very useful is the way to approach publishers or agents, it really is essential to do your homework as to which type of p/a would be suitable. For my part, I have used this lesson to walk around the bookshops and visualise my book on the shelves. From there, you can then see what authors write in a similar genre, what agents they then use and which publishers would be interested.

It is not a way to get published, but then in business you wouldn't set up a company without working out who your demographic would be, and writers need to think the same, which can be alien to most as I well know.

It's a very useful book and comes highly recommended.