Organize For the Season - Now that you know what's staying in your shed, you must consider when you use the items. You don't want to move a stack of gardening tools just to get to the snow shovels you'll need in the winter. If possible, dedicate one side of the shed to warm-weather specific equipment and the other to cold-weather equipment. This will alleviate any confusion on where items are and save yourself plenty of time when working.
If the clutter on your property says one unit isn't enough, but your wallet disagrees, supplement your main unit with one of the less expensive, smaller models. There are three main types of such units, all of which go by descriptive names. "Corner sheds" are made to fit precisely into a corner and run about 3 feet tall by 3 feet wide by 2 feet deep. Meanwhile, either a "vertical shed" (5 x 3 x 4) or a "horizontal shed" (3 x 5 x 4) may be just the handy outdoor storage building to fill your need for additional space.