One of the more difficult aspects of working in the service industry (waiter, housekeeping, drive-thru cashier, etc.) is the way other people don’t even acknowledge your humanity. It is normal for people to receive their services (which are often exemplary) without even stopping their conversation with someone else. Or worse, on their cell phone.
Being a gift to service worker is simple: Treat them like a human being.
Look them in the eyes. Give them your full attention. Treat them just like you would treat a friend you were talking to. Use their name. Be polite. Say, “Thank you.”
(Seriously, if you use a restroom that is well kept and you see the restroom attendant, say, “thank you.” You SHOULD appreciate a nice, clean restroom!)