Once a small part gets lost in grass or on floors, you can waste a lot of time looking for it. To find it quickly, put a nylon stocking over the end of your shop vacuum hose and fasten it with a rubber binder. Turn on the vac and play it over the area where it might have gone. If the part is there the vac will suck it up and hold it on the nylon so you can just pick it off.
When shopping or air conditioners, look for seasonal energy ratios (SEER) over 12 for central air conditioners and energy efficiency ratings (EER) over 10 for room air conditioners.