Sleeping Bag: Take it out of the compression stuff sack and store it in the big cotton sack it came in or in a king-sized pillow case. If it's really dirty, launder it first using a special soap like Nikwax tech wash. Use a front-loading commercial washer to prevent the damaging action of the agitator in top loading machines, turn it inside-out and select a cold gentle cycle. Run it through the rinse cycle again after it's finished to remove any extra soap. Dry it in a large commercial-sized dryer on a low-heat setting. Use tennis balls in the dryer to plump up down bags or take it out of the drier every 20 minutes and manually move the down clumps to break them apart. Dry until the bag is fluffy. Leave it out for a couple of days to finish drying completely, and then store it as above.
Water filter: Using clean water, rinse all parts of your filter thoroughly. Use a flexible brush to clean the hoses. If your filter can be backwashed, run clean water through it,and then sanitize with a weak bleach solution and let dry completely. If you have a ceramic filter, scrub gently with a clean scrubby and sanitize with a weak bleach solution by pumping the solution through the filter. Dry completely before storing.
Tent: Shake out your tent and make sure it is completely dry. If it's really dirty, you might need to clean it by setting it up and hosing it down. Use a soapy sponge to wipe the walls and floor and rinse thoroughly. Make sure poles are sand and dirt free. After it's dry, store loosely in a large pillowcase.
Hiking Boots: Brush off boots with a stiff brush. If needed, rinse with clean water while brushing. Dry completely out of direct sunlight and away from heat sources (this might cause them to shrink or soles to melt). After dry, put some baking soda inside to absorb odors and stuff with newspaper. If the leather parts are looking dry, moisturize your boots with special products to prevent cracks (consult your boots manufacturer for recommended product). Store them in a cool dark place until your next adventure.
Take care of your gear so it will be ready the next time you are heading out the door to explore wild places!