okie...
I've write up something like that before, but I don't know how good mine is... (so far... keep my fingers crossed, on those 2 incidents, there were no further trouble.)
you will need to prepare 2 copies (1 for you, 1 for him (or her))
you put down date, place, accident, involved parties, license plates and state, and a brief description of the accident (just like an accident report). (can insert a simple diagram also !!)
then you put down the driver license info of all the signing parties in there...
and you also put down the settlement.
saying noone is hurt, accident is minor, auto damage only and settlement is agreeded on and paid, and by signing, all parties give up their right for any further claims about this accident.
(of course you fill in the details...)
and if you're paying... I would say pay in something that got a receipt.... (some banks do certified check...) and put the form of payment (check # or something) in the doc.
and then you both sign both copies, and each keep one.
I honestly don't know how protected you will be (since there're always professionals out there that makes a living by these things...) but this is all I can think of at the time....
good luck.