Storage Garage space is commonplace for this purpose. The challenge with this is that often all of this becomes untidy and the place can soon become one big mess. With a bit of care and attention this need not be the case.
Before you do anything, you need to determine what needs to be stored. This can be done by first seeing what you need and what can be discarded. Do not throw everything away; there may be things that can be sold via a garage sale. This will give you money to buy items for the garage that you can use to make your garage look neater.
One way to go is to install cabinets in this room. Some of the items will be stored in the cabinets and other stuff will be placed elsewhere. Once you have decided upon this, you can make choices about the size of the cabinets. These cabinets can be obtained in plastic, wood or metal. They may also be mounted on the wall or be freestanding. If you have pesticides and chemicals then you would need lock up cabinets to keep these out of harms way.
Shelves are a nice addition to the cabinets. They can be home made for very cheap using plywood. Alternatively, pre-made metal or shelves can be used. The ceiling is a great place to contain items as well. Camping equipment and Christmas decorations can be kept here.
Using this space frees up the floor space for other items. Many items can be kept out of view if placed here. Plastic bins can be used to contain items and then placed in the rafters.
You can easily increase your Storage Garage space with a little eff