To repair couch springs, locate the loose springs and determine the actual problem. A spring could be too loose or popped out of its fitting completely. To fix loose springs, you need a hammer, pliers, staples, a staple gun and a flat-headed screwdriver.
Turn the couch over to enable you work from the bottom, and remove any staples or nails attaching the bottom fabric to the couch using a pair of pliers or a flat-headed screwdriver. Remove the fabric from all edges except the back edge of the couch, exposing the inside of the couch.
Locate the loose springs and determine the problem. Use a pair of pliers to bend or twist the loose springs back toward the fitting, and slide the end of the spring into the middle of the fitting. Tie the springs in place with a long metal wire by securing the wire onto the springs all the way around the couch. Tighten the screws or hammer the nails holding the fitting in place to tighten the springs. Inspect the other fittings along the back and front sides of the couch to tighten any loose ones. Put the fabric back in place and secure it to the couch using a staple gun. For larger problems such as broken springs, fittings or boards, seek the help of an upholsterer.