Got to give them something to work with... throw out a story line or an opening, synopsis, so they can see your writing style and if you have a good idea... around here, creativity and the ability to communicate effectively in written words is what is considered sexy, appealing..
Also may want to post this in the seeking RPers & inspiration thread. It will get more attention that way. Also a good idea to mention if you are looking for male, female, both, any. The more information you give the better than chance some one will respond.