To answer a few commonly asked questions:
-If you’re writing fiction, you do have to write a complete manuscript before submitting it anywhere (and I will tell you right now–finishing is the hardest part!). The way it generally works is, you write a book (and edit/polish it as much as possible), then research literary agents to find someone interested in the genre you’re writing in. Most agents have profiles on their agency websites stating their preferences, but many of them have profiles listed on Agent Query (http://www.agentquery.com/).
-If an agent (hopefully!) loves your book, they might offer representation right away. However, sometimes they’ll ask you to revise the book and resubmit, or sometimes they turn you down, but usually for a good reason (reasons I was turned down for various manuscripts: the agent didn’t feel they were right for the project; the agent didn’t ‘fall in love’ with the book; in the opinion of the agent, the book needed heavy revision).
-Once you have an agent, it’s their job to sell the manuscript to a publisher. A reputable agent will NEVER ask for money up front. They make a commission after the sale.
-Yes, you need a critique partner. Preferably more than one. They don’t need to be published authors, but it helps if they write in the same genre that you’re writing. I met one of my critique partners on a writing message board, and the other one on Twitter.
Here are links to a few blogs and websites I read while trying to figure out how to get published. ALL of the information you need to find your way in the publishing industry is available here if you look for it:
Writing Message Boards
The Absolute Write Forums: http://absolutewrite.com/forums/
The Blueboard (children’s books only, picture books to young adult): http://www.verlakay.com/boards/index.php
Agent Jennifer Laughran’s Blog: http://literaticat.blogspot.com
Agent Mary Kole’s Blog (children’s books only): http://kidlit.com
Agent Kristin Nelson’s Blog: http://pubrants.blogspot.com/
Websites For Finding An Agent