A storage shelf in the attic will help to organize and make extra room up there. An attic can be an area that can easily get disorganized, but here are a few ideas to help manage the mess.
1. Work with What's Up There
Most attics have exposed wood frames. Use these as the support for the shelves. Measure the distance between these beams. Then buy big sheets of wood (any kind will do, even cheap plywood) and cut them to sit on top of these beams. Drill the wood into the frame. You have just created more storage room in the attic and made more room by lifting the stuff off the floor.
2. Stack-able Containers
Perhaps the easiest way to add space going upwards is to buy stack-able plastic storage containers. Get them clear so you can view what is in there without having to move them and open them. It would also be a good idea to buy coordinated lids to match what is in there. Use orange for Halloween, red for Christmas, pink for baby girl clothes, blue for boy, etc.
3. Freestanding Shelves
If you do not have rafters to work with, you can cut and make shelves out of wood. Again, any cheap, strong wood will do since it won't be seen. Buy L- brackets. Make the shelves as wide and deep as you need them to set your things on. Mounts the L- brackets to studs and drill the shelf into the wood.