I personally have never had a rep because of the costs involved. A traditional sales rep will want a percentage of all current house accounts and a larger percentage of what they bring in. This is in addition to covering expenses such as promo materials, portfolios and other marketing materials. I could never bring myself to give a percentage of my sales from in house clients - some of whom I have been nurturing the relationship for years. All the larger most successful photographers have them - so maybe I am missing something.
A less tradiotional sales rep would be Wonderful Machine (http://www.wonderfulmachine.com/) They rep photographers all over the country. Contact them for details.
I have limited experience with Reps and I've always thought that they find you. You can send promos to them and try to attract one that way but I think it's best to continue shooting and build your own business. I started working with one a couple of years ago but found that she was less connected than I, if that is possible.
I am thinking about getting a rep for my work. I am not sure how to go about it. Does anyone have experience with reps? What should I expect from them? What kinda fees? Any good suggestions on who to go with? You can see some of my work www.codyphotography.us and also http://codyphotography.prosite.com