You can make your topic however you'd like, within the rules of course. Short and to the point, or lengthy with several paragraphs. I'll show you mine, as an example. This is my request thread.
At the top, I list everything important for my partners to know, such as:
where you prefer roleplaying (threads, PM's, emails, etc)
what relationships you like (female&female, male&female, male&male
how often you can post, or how much you post on average
likes/dislikes/kinks
Then, I list possible character and roleplay ideas with a plot included. You do not have to follow this set up at all.
Just take a look at some other request threads and get an idea of how you want it set up. Good luck!