Remove everything from the garages, including storage shelves, your work bench and other fixtures. This makes it easier to install the new flooring over the entire surface all at once.
Inspect all areas of the garage floor. Look for cracks, leaking or seeping moisture on the floor.
Patch any small cracks using a combination of Portland cement and water, with just enough water added to make a paste. Wet the existing concrete with water for several hours so that it doesn't draw out the moisture from the patching material. Use a putty knife to fill the crack and smooth the top.
Sweep and scrub the floor to remove any grease or debris before redoing the floor. Rinse the floor and let it dry completely.
Paint the entire floor using an epoxy garage floor paint. The epoxy coating protects the floor and makes cleanup easier when you spill things like oil or water on the garage floor.
Install interlocking rubber floor tiles made for garages if you prefer this over paint. Another option is to combine the paint and tiles. Paint the entire floor with the epoxy paint; then install the floor tiles in a particular area of the garage as desired.