Request and Offer form
Request and Offer form is appropriate for any arms-length transaction where it might be important to review the contract later. This includes a social contract. Without this form, more social capital than necessary is at risk. The formality is an important form of hedging via etiquette - if things go wrong, they are restricted to only that one matter.
To put something in this form, state it as a Request. Anyone who wishes to respond will develop that request further into an Offer. If this is satisfactory, the request will be withdrawn and the offer accepted. If not, a Counter-Offer will be created but the original Request will remain visible for other competing Offers to respond to it. All of this should be recorded reliably. A legal contract almost always follows this format, for exactly the reason above: if things go wrong, issues are contained. They do not generally turn into a reputation war or something.
One can look at wiki edits as following this form. An open link is a kind of request, and an attempt to create a viable page is an offer to close that link. If it is rejected, the page might be blanked or even deleted. A second offer can then be entertained, etc.. See also Unanimity Minus Two.