Bel Booker wants to help you write your RFPs, not for free, but there's some great tips on Eventbrite's blog.
Suppliers need a clean and detailed RFP in order to know exactly what to deliver.
On the flipside, planners want a response no matter the detail or perceived quality of the RFP.
You can read a bit about this existential battle from Suppliers Behaving Badly or Planners Behaving Badly from Shawna Suckow.
For Tips on Writing Your RFP, head to Eventbrite.