Write or type up the date on the agreement to establish an effective date. List the parties involved in the agreement, using full business or individual names and titles. For example, you may title your business as the "Service Provider" and the customer as "Customer."
If you run a business as a sole proprietorship, it would be appropriate to be identified in the contract as John Jones doing business as Jones Plumbing. If you organized your business as a Limited Liability Company, identifying your participation in the contract by your name could remove any personal liability protection that an LLC provides. Similar issues can arise with a partnership if each individual is identified as a party to the contract.