I get this question frequently from our staff. I'll tell you what I tell them. It is your job to serve the client even when they're rude, smell bad or don't have a clue what they're talking about. Unless they pose a threat, they don't have to please us, we have to please them.
As for privacy, treat it like a drive up client with a passenger in their car - if they ask a question jot the answer on a piece of paper and hand it to them.
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If you approach life with pure logic you can avoid almost all of the fun.