I found this informational post over on the blog of Diane Lockward. It sounds like she has been on both sides of the poetry contest game - she has entered many and served as a judge for one. Out of her experience, she shares several useful recommendations for contest entrants. Click the link below to check out this resource.
http://dianelockward.blogspot.com/2010/07/some-thoughts-about-poetry-book.html