As a preliminary, I feel obligated to mention that writing a contract only protects yourself on paper. The real world has such complexity, and with innumerate contingencies, that any contract will fail to enumerate them all. Establishing an explicit contract often also cements distrust between parties, due to its impersonal nature. The contract just gives a written record of what the parties agreed to, so that, should the end up in arbitration, others can more readily see the terms of the agreement. Because of these factors, writing a contract is a costly affair.. So, what should go into it?
Suppose two parties, even after recognizing the costs, still wish two write a contract. They agree on many standard items and write them down (or borrow them from a template), but the parties still have some remaining details about which they disagree. Each has an interest in investing a some time to sort out these details in order to avoid unpredictable future conflict. But how shall they obtain an agreement on what actually gets written down?
I thought of one approach: holding a silent auction. For every issue on which they have a disagreement, they can write down all the mutually-exclusive options and hold a silent Vickrey auction.