Some garages like mine are small and we don't always have a lot of room to get out of our vehicles. Purchase a pool noodle, slice it down the middle. Attach half of it on the right wall, and the other half on the left wall. Now when you open your car door you won't ding the wall and the wall won't ding your car door.
Have you ever had a screw stripped? Well use a fat rubber band, place it over the screw head and then you can screw or unscrew. The grip from the rubber will help screw it in or out.
Most people store their cleaning supplies under their kitchen or bathroom sinks. Try using a tension rod under the sink to hang some of those spray cleaners. This will make more room for boxed items like trash bags.