Establish ownership rights to the work. Even in service situations, a product is sometimes the result of the work, so you should also include which party retains ownership rights. For example, the copywriter can state that she turns over all rights to the writing of the brochure to the customer and that she makes no claims of ownership to the writing once the customer pays for the written product. Add signature and date lines. Be sure to provide a space for each party to sign and date.
You may want to have an attorney review and make suggestions on a template of your business contract. An attorney can pinpoint issues for your particular business that you may need to include in the agreement. You can use a business agreement template and modify it to fit your needs, rather than writing the agreement from scratch.