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.
Clean It Out - With any organization project, you'll want to remove everything to start fresh. This goes for your shed as well. Toss any old items or trash to declutter your space. If there anything you haven't used or your family has outgrown, now might be the time to donate or sell that item. Though removing everything from your shed might seem counterproductive, it's better to see what you have to store before you create new systems for it.