A number of large companies we work with also have this approach. There must always be offer, acceptance, consideration, intention to create legal intentions and certainties of conditions. This can be best demonstrated in a written contract, but in many cases, when the essential elements are in place, a binding agreement is concluded, that there is something in writing. Even if no full deadline has been agreed, try to set as many conditions as possible agreed in a short interim contract or set binding terms. Of course, this doesn`t tell you everything you need to know about contracts, but it`s a good start.