Agree on the pay scale and schedule. Most carpenters have a set hourly rate for their work, but there might be negotiating room on larger jobs. The schedule should include a plan for you to make payments when certain job milestones are reached. Avoid terms such as "half of the work." Be specific about what is to be done before money will exchange hands.
Choose the materials. If you use a through-rate contract, the carpenter will purchase the supplies and pass on the cost. With this type of contract, make sure a detailed materials list is an addendum to the contract. Another option is a labor-only contract; with this option you purchase the materials and pay the carpenter only for her labor.
Complete a time line. Most construction projects involve some degree of uncertainty, but your contract should set out a start date and estimated end date as well as any needed midrange dates. Also include a clause for how to handle changes in these requirements.
Set up house rules. For small jobs, the carpenter probably will not be in your house for more than a couple of days. With larger jobs, though, be sure to specify the hours during which the carpenter may work, such as "before 7 p.m." Also add in any concerns you have about visitors to the job site, smoking and other rules about your home.