An Agreement Between States Is Called
Who Can Sign - For partnerships, only general partners can sign a contract, not a limited partner. For LLC's, a managing member or a hired manager can sign. For corporations, the company's president or chief executive officer is presumed to have the authority to sign. For an organization or association, a board president would have the authority, but may require a vote of the governing board to approve the deal.
Describe the other party's obligations in detail. In the case of out brochure writing example, this might explain that the client is responsible for providing the copywriter with business information in a word processing document to describe the business and the information to be included in the brochure text.