A weekend afternoon devoted new to sprucing up your outdoor furniture will that the pieces will be ready when needed and will help extend their life considerably.

Usually, the first thing needed is a good cleaning or washing. After wetting each piece with water, use a sponge or soft-bristle brush to scrub them with a detergent solution. Hose them off with plain water. If stubborn stains or dirt streaks remain, use a concentrated spray-on household cleaning liquid (undiluted) on these spots.

Spray it on, let soak for about a minute, then scrub again with the brush. One plastic-covered cushions and similar vinyl upholstery, some stains may be difficult to remove, so buy one of the special vinyl cleaners sold by marine-supply and auto-supply dealers and use it full strength. This may work when all else fails.

After cleaning each piece, wipe it dry, then check all bolts, screws hinges and other hardward for signs of corrosion. Where practical, replace corroded hardware with brass, aluminum or galvanized equivalents. Or use a rust-removing liquid to clean the corrosion, then coat with clear lacquer or paste wax.

While checking for corrosion, tighten all bolts, nuts, screws and other fasteners with a wrench or screwdriver, and make sure none is missing. Replace corroded fasteners with new rust-resistant ones. Spray all hinges (on folding chairs, etc.) and other movable or adjustable parts with moisture-displacing lubricating spray to keep them moving freely and protect against future corrosion.

If chairs or lounges have torn cushions, they can be mended with vinyl repair cements now available in most hardware and houseware stores. For large rips, a patch of similar material should be cemented behind the tear (on the inside, in the case of a cushion) to reinforce it. The cement serves to fuse the torn edges of the plastic.

Many pieces of lawn furniture have seats and backs covered with plastic webbing. Constant exposure to the sun eventually causes this webbing to deteriorate. A chair can be rejuvenated by replacing the webbing with new material, available in hardware and houseware stores and in home centers. The webbing comes in many colors and lengths. To cover a typical chair costs less than $2.

To re-web a chair or lounge, first remove all the old material, but save the screws or clips that secure it to the frame. Cut new lengths to fit, allowing enough to make folds at each end, as illustrated, then fasten the new webbing in place. Be sure to use washers under each screw head.

In some cases, special clips have been used instead of screws, so note how these fit as you take them off, then replace them in the same way. Bent, corroded or broken screws or clips should be replaced. (The dealers who sell the webbing also sell the hardware for it.) On wood-frame furniture the webbing is usually secured with tacks or wood screws; be sure the ones you use are rustproof.

Here are some additional pointers on sprucing up some of the more common types of outdoor furniture:

Aluminum: If it has lost its luster or is pitted, use a metal polish designed for this metal. Pit marks, if not too deep, can be removed by rubbing with fine steel wool. When the metal is clean and reasonably bright, protect it with regular applications of a good quality paste wax. Hose pieces frequently during the year to remove dirt.

Aluminum furniture often has steel fasteners or rivets that rust. If they cannot be replaced easily, clean and protect them as described above. On folding pieces, keep joints coated with protective lubricating spray that contains Teflon and displaces moisture.

Redwood: Although this wood theoretically needs no protection against exposure, it should be coated with redwood sealer each year. After cleaning, sand off dirty spots and apply two coats of sealer. If the color is not needed, use clear sealer. However, if the wood is gray and dingy looking and you want to restore the color, use a pigmented sealer that has redwood coloring added. To minimize splitting caused by water absorption, coat the bottom ends of legs and all exposed edges.

Make sure bolts and other fasteners are tight, and replace rusted ones promptly to keep from staining the wood. If rivets work loose, tighten them by using two hammers, one on each side. Hold the heavier hammer in the back and strike the other end of the rivet with the second hammer.

Painted wood: After washing, scrape off all areas that are peeling or starting to crack, then allow the wood to dry thoroughly. Coat bare spots with wood primer, then sand the entire place and apply one or two coats of outdoor enamel. If hardware shows rust marks through the paint, touch them up with pigmented white shellacbase stain killer, then paint in the usual manner.

Wrought iron or steel: Use steel wool, sandpaper or wire brushes to remove rust, paying as much attention to the undersides as you do to the visible parts. Spot-prime the bare areas with a metal primer sold for use on rusted areas. Allow to dry, then coat with one or two coats of outdoor enamel or one of the special rust-resistant metal coatings sold for that purpose. If the feet of the furniture leave rust marks on the patio, cover the bottom ends with rubber crutch tips, or cement rubber pads to the bottom of each (use waterproof rubber cement or silicone rubber as an adhesive).

Rattan and wicker: Wash thoroughly and allow to dry for several days. Moisture won't hurt this material, but sun causes it to dry out and crack so it absorbs dirt. If the pieces will be exposed, coat with waterproof varnish, using a paint sprayer or a spray can of clear varnish. If bindings tear loose on rattan or wicker, wet with water to soften, then refasten with rustproof tacks or staples.