Keep your furniture on a covered porch or patio, away from heat sources such as vents, outdoor fireplaces and fire pits, which can dry out the canes.
Remove any cushions on the furniture and set them aside where they will stay clean and dry. Use a vacuum with a furniture attachment to vacuum your wicker furniture on a monthly basis to remove any dirt and debris. Use a spray bottle with water to lightly spray the underside of a sagging seat to tighten it up.
Wipe the wicker furniture down with a damp cloth after vacuuming. Apply a quarter sized amount of oil soap onto a damp cloth, and work it into the wicker. Reapply more oil soap to the cloth as necessary. Rinse the furniture with a clean damp cloth, and let the furniture dry completely.
Apply a quarter-sized amount of linseed oil onto a cloth, and work it into the wicker. Use a clean cloth to wipe off any excess oil. Replace the wicker furniture cushions when the canes are dry to the touch.
Store your wicker furniture during the winter months in a heated space with medium humidity to prevent the canes from freezing and breaking. Put a quart of water into a bowl and leave it in this space. Refill it as necessary to keep the wicker furniture supple.