Review the theater needs. Ask the director to work with the set builders in concert with all other theater workers.
Define the parameters of the set and what props need building. Look over the script and see if there are hints that might provide a path from which to work. Carry a small notebook around to jot down ideas for types of props if the creative director is cloudy on the specific props needed.
Buy the material for the props. Most all of the materials needed for prop and set building are available at hardware and home improvement stores. Plywood, screws and paint are common materials.
Inspect all of the construction tools and space to ensure a smooth workflow. Be certain all saws are sharp for woodcutting. Prepare and construct props carefully.
Make wood cutting templates for items that need more than one copy made. A template is a guide used over and over for consistent copies. Typically paper or cardboard makes proper templates.
Read woodworking books that offer ideas for theater and Halloween prop making. The processes for both are very similar and contain instruction for drawing, cutting and assembling wood props for many uses including theater.