Take measurements of your front porch. You will need the width and length. Measure from the left side to the right side of the porch to get the length. Measure from front to back of the porch for the width. Write the numbers down and go to the local home building center for supplies.
Select the pre-formed rails and balusters you want. The balusters are the supports that connect the top and bottom rails. The railing will come in 2-inch-by-6-inch sections and the balusters are in 2-inch-by-2-inch sections. You can also use pre-treated lumber, which can be cut to size for this project.
Put the balusters in position on the bottom railing. Drill preset holes through the baluster holes into the rails. Secure the balusters with the galvanized screws, screwing up from the bottom of the rail. Using the hot-dipped screws will prevent rust and corrosion from the exposure to the cold and wet weather. This also helps keep the wood from rotting around the screws.
Put the top rail on top of the balusters. Match up the ends of the top and bottom rail using a level set up against the ends. Connect the balusters to the top rail using the same method as described above.
On each end of the rails attach a 2-by-4 board for a support brace with nails. This brace will attach the rails to the porch support posts. Drill two pilot holes in the 2-by-4s. You'll place the lag bolts here when you attach the brace to the posts.
Place the rail into position between the posts. Use wood blocks to support the rail while you attach the rail to the posts. Attach the lag bolts with a ratchet wrench, making sure the bolts are snug into the post. Sand down any rough edges and paint the railings and supports a desired color.