Add storage spaces to your deck.
A space at least 2 feet high under the deck offers plenty of room for storage. Grade-level access (through a door), isn't handy with a 2-foot space, however, because you would have to crawl under the deck. Instead, build an access hatch so you can lower things into the storage space from the deck.
To create underdeck storage, attach a storage box to the joists before you install decking, and make the hatch from decking cut to fit the recess. Cut a hole in decking boards or install flush lifting handles so you can lift the hatch out.
If your deck is raised 4 or more feet off the ground, entry through a door is practical. In that case, build removable skirting sections or hinged siding panels.
Construct latticed skirting, but make one or more of the sections removable. Fasten the lattice to the back of a 1x4 frame cut to fit the section. Install 2x stops inside the opening for the lattice to rest against. Fasten sliding bolts to the panel at the corners and the shoes on the bottom frame. Slide the bolts to keep the panel in place.
To make an access panel for underdeck storage (or a hose bib or electrical outlet), cut the decking flush with the inside of the joists. The opening's size will depend on what you're accessing -- storage space, hose bib, or electrical outlet. Cut two pieces of decking to fit in the opening and cleat them together with wood scraps. Drill 1-inch holes near one end of one board and the opposite end of the other. Nail 2x4 cleats to the joists to support the hatch.