There are many ways depending on where you are at. No matter what level you are at you can use the writing tools to help organize your thoughts and overall book; you can gather feedback from trusted friends or complete strangers; you can browse the forums for topics that are relevant to writing; you can find a graphic designer for your cover or an editor for you book.
For those who are advanced, you can (and should) print a "finished" book to send to publishers and agents. This not only shows your ability to complete a work, but your professionalism and resourcefulness.
Of course, with our prior contacts in the writing and publishing business, agents and publishers will undoubtedly be browsing our site in search of new works to pick-up.