A recliner is not only an effective way to relax, it often has an emotional connection for the owner. The chairs usually last a long time and get associated with various time periods and emotions in a person's life. Repairing the chair is, therefore, often more appealing than replacing it outright and also saves money in the process. One common problem with a recliner as it starts to age is sagging.
Unzip the covers from the cushions and remove them. Slide them back on over a fresh cushion of equal size. Fresh cushions are usually available from furniture stores or can be ordered from the original recliner manufacturer. Another option is adding fresh stuffing to the existing cushion to increase its support inside of the cover. Broken-down cushions are often a source of sagging.
Tighten the screws and bolts inside the chair with a screwdriver or Allen wrench. As the chair loosens with age and wear, it loses support. Tightening the joints again helps restore support. Access these components by putting the chair in its "recline" position and then looking underneath it.
Add a piece of plywood under the seat cushion to add firmness to it. The board should be slightly smaller than the cushion so it isn't visible with the cushion on it.
Cut open a seam in the side cushions with a razor blade. Stuff the opening with cotton, down feathers or furniture stuffing to plump up the sides and reduce sagging. Sew the seam shut with a sewing kit when you finish.