Go to the reference section of your library and get the copy of the latest (2007 or 2008 if now available) 'Writers and Artists Year Book' that lists the publishers of the genre you are working in.
Call and see if they accept un-solcited m/s. If they do, send off the info and wait for a reply.
Send the docs and keep copies.
Use the web as well for info from such sites as bloomsbury.com which has stuff for aspiring writers to get to gripe with how to approach publishers, if you need an agent, about copyright issues, about how to submit transcripts - you do not send a copy of the book by the way - you send a synopsis, etc etc.
Hope this useful and best of luck!