1. CLEAR OUT
Weed out all the junk you don't need. Keep only what you use; give away what you don't, and throw away what's broken and taking up precious space.
2. MAKE A PLAN
Treat your garage like any other room in the house. Take measurements and draw a floor plan to help you visualize what will fit and where it can be placed, just as you would for a kitchen or a dining room.
Decide what items you'll use often, like garbage bags and cleaning supplies. These things should be kept nearest the door. Next, map out space for seasonal equipment: lawn mowers, weed-trimmers, snowblowers, etc. Avoid planting big items, such as lawn mowers, in a corner where they'll chew up space. Try to park them under a shelf unit. And be sure to clip ladders, shovels, rakes, and other garden tools into a wall rack off the floor.
Finally, get seasonal space hogs such as snow tires, kayaks, and bikes off the floor. These items should be relegated to walls or hung from the ceiling. A hoist pulley system (available at home centers or online) that operates like the cords on window blinds and has clips or straps to hold large items can be installed directly into ceiling joists.
Keeping things in containers not only lets you get them off the floor but keeps them clean. Transparent stackable bins conserve space and also allow you to see their contents. Always label opaque containers so you know what's inside.
Designate a safe space for hazardous materials like fertilizers, pesticides, and paint, so kids can't get into them. Sharp gardening tools should also be hung up out of reach, and chain saws and other sharp tools stored in locked boxes.