Let's be realistic: A garage is a storage area for many things that are used exclusively outside. It's not supposed to be immaculately clean and 100 percent dust-free. It can, however, be a relatively clean area that feels good to use.
To achieve this state, sweep and (if possible) hose down the floor. Swat down any cobwebs you find. Use a clean rag and water to wipe down big surface areas to minimize fine dust that tends to settle on things. Spray down lawn furniture. Launder outdoor pillows, cushions or towels to get rid of mold or mildew (a washer's hot water setting is best).
If you're leery of using chemical cleaners for health reasons, try making your own eco-friendly multipurpose solution that's free of harmful chemicals or irritants. Simply mix water and vinegar together; the tougher the job, the more vinegar you should use (the odor will disappear when the solution dries). Use it to clean the inside and outside of windows and other surfaces.
If there isn't enough room to store all your household cleaners indoors, go ahead and keep them in the garage. Since you will probably access this collection regularly, keep these items together on a shelf or inside a cupboard or bin that's about waist-level for easy access.