Frame a basic open porch with a post and beam approach. Install posts or build piers at the outside edge of the porch, install a 2-by-6 inch ledger board or support on the house and set beams around the edges to support a roof. Use as many posts as needed for the depth of the porch, typically spaced no more than 8 feet apart. Leave the sides open.
Use a variation of stud wall framing for an enclosed porch. Build walls of 2-by-4 inch stud lumber, with studs spaced 24 inches apart or to conform to the windows or screens to be installed. Make top and bottom plates: fasten top plates to a frame set between outer posts or columns and the house wall. Fill the sides with pre-built windows or screens or use combinations that can be converted from solid pane to screen.
Build half-walls with another variation of stud framing. Install top and bottom plates with 2-by-4s. Put vertical studs at the ends and at no more than 6-foot intervals between the ends. Make 2-by-4 caps to fit between the studs, with 2-by-4 or 2-by-2 balusters or posts spaced 8 to 12 inches apart between the vertical studs.
Make a simple shed roof by installing a ledger board on the house and connecting it to a similar board across the outside posts with side bands. Use 2-by-6 inch boards for this frame. Set the ledger high enough above the outside edge to allow a slope of at least 1 inch per foot. Cut rafters to fit between the two end bands and hang them with metal rafter hangers. Space the rafters 24 inches apart.
Use prefabricated trusses for the easiest gable roof. Mark the tops of the walls or outside beams in 24-inch increments. Raise the trusses to the roof and nail them in place through the truss ends to the wall tops or beams. Fasten the first truss to the house wall with long lag bolts that go through the wall into studs or other house framing.
"Stick build" a roof frame by cutting rafters from 2-by-4 inch lumber. Use a framing square to mark and cut rafters to any desired pitch or slope. Install rafters with a ridge board between the outside and the house wall to hold the tops of the rafters and secure them laterally. Fasten one set of end rafters to the house wall with lag bolts.