Also, look to writing groups in your local community, but be cautious if you are writing genre fiction. Not everyone in the group may be familiar with the genre, and sometimes you may find members critiquing the genre instead of your work. Go to the bookstores and study the shelves. Become familiar with the best seller lists. This will tell you what types of books editors are buying.
Writing is a business.
From a marketing standpoint, it is helpful if you can say you have written a book that is similar to a Dean Koontz or a Jayne Ann Krentz or a Julie Garwood. There is a great division of opinion on this issue and some of my peers would disagree, but I generally recommend approaching publishers first, simply because I've known too many writers who have lost years waiting around to hear from agents. Some publishers, however, indicate that they will not accept unagented submissions. If your query letter is exciting enough, maybe they'll make an exception. Some publishers indicate they won't accept simultaneous submissions.