It's amazing what a fresh fabric can do for a dining room chair. Many dining chairs you'll find at thrift stores have removable seats, which makes this do-it-yourself furniture project even easier.
Unscrew the seat and remove it from the chair. Use a screwdriver and needle-nose pliers to remove staples from the old fabric. Pull off old fabric; using it as a template, cut a covering from the new fabric. (If you plan to add new cushioning, cut the new fabric large enough to accommodate any added fullness.)
Before you re-cover the seat, paint the chair, too. Watch the video below to learn how.
If the seat is sturdy and the cushioning doesn't need to be replaced, move on to the next step. If you need a sturdier seat, use the existing seat to measure, mark, and cut a template on thick cardboard. Use the template as a guide to cut a new plywood seat.
To replace the cushioning, use the cardboard template as a guide to cut foam padding for the base; the padding should be 1–3 inches thick. Remove existing cushioning. Layer the new foam padding on top of the seat, aligning edges. Cut a piece of batting, leaving extra on each side to attach it to the underside of the seat. Wrap the batting around the top and sides of the foam and wood seat; turn the seat upside down. Using a staple gun, secure the batting to the underside of the seat, pulling and smoothing as you go. Trim excess batting.
Place the seat upside down on the wrong side of the new fabric, making sure any pattern is centered on the front. Using a staple gun, staple each side once in the center, pulling the fabric tight. Working from the center outward, staple one side, pulling the fabric tight. Repeat on the side opposite the one you just finished. Repeat on the remaining two sides. Fold corners into a pleat and staple. As you work, check to make sure any patterns are straight and there are no wrinkles on the front. Trim fabric.
If desired, finish the seat bottom by stapling plain fabric to it. Use screws or corner braces to secure the seat to the underside of the chair.