I don't have an exact idea, but I have a few tips on what people would like (this mostly applies to literate role players looking for long-term Rps, such as myself).
1. Make people give Rp samples. This lets other literate people know that they won't be role playing with illiterates.
2. Make a plot for it. Without a plot, the Rp will be no better than any others.
3. Have the Rp based for canines. Of course, if you like, make it for felines and canines. The majority of feral heartans tend to be on canine characters.
4. Give it a website and/or a map. Maps keep illiterates out and a website keeps everyone up to date without having to be in game.
5. Invite your close friends first. With that, your Rp already has a start and they can invite their friends.
That's all I can think of at the moment. I hope I helped a bit. ^^'
Wish you the best!