Porch swings are sold at most home improvement warehouses and garden centers; take a pad of graph paper and a digital camera on an ideas-finding trip, then transcribe your notes into a neat schematic while the examples are still fresh in your mind. Add the desired dimensions, including the dimensions of the lumber -- for instance, the seat slats may be 1 inch by 2 inches wide -- as well as the required lengths. Have a vision of the cushions that will be on the porch swing; if you intend to use 36-inch square cushions, the seat base must be 36 inches deep and a multiple of 36 inches wide. Wider, deeper seats make for better lounging and napping.
Once the schematic is finalized, work out a purchasing list for raw materials. All the wood should be “finished,” meaning it has been planed and sanded by the provider; people come into contact with all parts of a porch swing at some point, so splinters are not desirable. The use of screws, as opposed to nails, makes for a neater and sturdier project; buy deck screws that are treated to resist the elements. Exterior wood glue is recommended for joins in the framing.
You will need wood for the seat frame, the seat slats, arm supports and arms, the back assembly and a support frame if the porch swing is not to be suspended from a ceiling. You will need filler for screw and knot holes, sandpaper, and either lacquer or primer and paint. Remember to add the hardware and chains that will eventually be necessary for hanging the porch swing from the ceiling or its A-frame support structure.
When working to a complex schematic, always note an identifying number somewhere on each piece; use a pencil, scribe lightly and make the mark where it will be obscured by another piece of wood later in the project. Stick to the plan precisely: Shortcuts seldom shave any time off such projects; rather, they usually cause unforeseen problems and result in time-consuming additional work.