First, let me provide you with this awesome link that our design team has been adding to! It's some templates for request threads and a definite option if you want something a bit more fancy!
Some of the biggest things to include in your RT are:
What you are looking to play - Stories, pairing etc
How you prefer to play - Threads, PMs, Discord etc. This can also include your tense
Some people also like to include an F-list.
Really there is nothing required for a request thread, it's what you feel happy with as there is no wrong or right way to do one.
Edit: Something I personally did was look at how others structured theirs and found several to try and emulate ^-^ Hope this helps!