Describe your obligations, including the service you must perform to fulfill your obligations under the contract and be as detailed as possible. For example, if you are writing a marketing brochure for a customer, describe the length of the brochure, the purpose of the brochure and establish that you are only responsible for providing the text, and not the layout or design, for the brochure.
Legal Contracts - Under state laws, only a few category of contracts must be in writing, such as a mortgage contract or contracts covering more than a year. It's still a good idea, however, to have a written agreement for business transactions beyond an ordinary sale of goods. There is no law requiring a lawyer to write your contract. If the transaction is relatively simple, the contract can also be simple. But you also have to pay attention to certain details to avoid issues arising later.