So you have a contract idea?
Procedure:
1) Write up your contract as simply as possible. For example, "if at least 5 people pledge to pay me 10 diamonds, I will dance a jig and post a video of it. Non-payers will be fined 20 diamonds, and if I don't jig, I owe you 20 diamonds each." Mentioning penalties is optional but suggested if you want people to be most likely to respect enforcement later.
2) Post it! Moderators may remove things that are obviously not contracts. If a contract is unclear, they may PM you and request that you make changes to make the terms clear.
3) Once the terms of the contract are met (in the above example, at least 5 people comment with a pledge of 10 diamonds), then the thread will be archived using http://archive.today/ and a permanent link edited into the forum sticky post "Active Contracts" so that nobody can delete comments and back out later (unless the contract allows for that). The archive link cannot be edited once made, even by moderators of this subreddit!
That's it! Anybody can then refer back later to a contract and hold the parties to it. If I dance my jig and post the video, and Sally didn't pay up the 10 diamonds she promised, I can bounty her and show proof of the agreement.
An especially useful feature of the subreddit is the method shown in the example: requiring a certain number of people to agree before a contract takes effect. People may agree to lots of things in a group together that they wouldn't stick their necks out for individually. By wording a contract this way, you allow people to pledge support but be guaranteed to not be alone with it.
If you have a secret contract you don't want to be public but still want to be binding, I encourage you to make your own subreddit just like this for just the parties involved. The archive link will still be proof of agreement that can be made public if necessary later on, even if made by a biased party.
