In a contingency contract, the task defines exactly what behavior a person must engage in to access the reward. It should include what needs to be done, who must do it, when it must be done and details with how it must be done. It should be very clear and specific for all parties.
Contingent contracts, like contingencies themselves, cannot occur unless a certain condition is met. For instance, the sale of a home cannot take place without a prior home inspection, and an aircraft cannot leave the hangar without a thorough walk-around inspection by the pilot.
A contingency clause should clearly outline the conditions, how the conditions are to be fulfilled, and which party is responsible for fulfilling them. The clause should also provide a timeframe for what happens if the condition is not met.
There must be a valid contract to do or not to do something. The performance of the contract must be conditional. The said event must be collateral to such contracts and the event should not be at the discretion of the promisor. These are some rules that have to be followed for a contingent contract to be enforceable.
In the case of conditional contracts, conditions that need to be fulfilled are certain, i.e., bound to happen, which is not the case with contingent contracts, as such conditions may or may not happen.