The biggest enemies to your gear are sunlight and abrasion. When you are not using your gear it should be stored in a cool, dry, dark place. UV exposure will deteriorate the strength and cosmetic appearance of your equipment. Try to keep your gear as clean as possible. Avoid leaving it in the dirt or stepping on it. The Kevlar lines are susceptible to kinking and can be damaged if pinched against rocks. The kevlar core may break while the sheath stays intact, hiding the problem. Do not step on your lines!
If you feel the need to clean your glider, use a damp sponge and some warm water. Avoid washing it with detergent or soaking it (eliminating salt water may require a soak). This may have a detrimental effect on the UV coatings designed to protect the glider. If it is a little dusty try kiting it in a grassy field. This should remove some of the dust. You can also kite the glider upside down or shake it out to remove the dirt and other debris from the cells. Some gliders have velcro ports on the wing-tips which will allow you to clean debris from cells.
Other items you should avoid having around your glider are solvents of any kind (including oil and gasoline), extreme heat, damp storage, and sharp or abrasive objects. Watch out for sunscreen, the oil can leave a stain.