Anyone who is likely to be asked for a loan would do well to figure out a blanket response, whether it's "I really can't do that for you" or "I don't loan money to family," he said.
"You've got to come up with some level of preset rationale, a consistent message to everybody," Post said.
And you shouldn't feel bad for saying no. "You're not the one who created the negative situation," he said. "They did, by asking you for money."
"How do you handle a relative who wants to know the cost of everything you buy? Last night we paid for dinner (for) 14, since it was a celebration of our son's birthday. This relative asked right out what the bill cost. I pretend not to hear the question but it's getting annoying. How do I put this person in their place gently but get the point across … 'it's none of their business'!"
Pretending not to hear rude questions is a time-honored way of dealing with nosy people, Post said.
Unfortunately, people insensitive enough to ask may be insensitive enough to persist. In that case, you can offer what Post calls a "nondescript" answer. Something like, "It's a reasonable bill, and I'm glad I could pay for it."
Other well-tested responses include changing the subject or simply saying, "I prefer to keep those details private."
"What do you do when people overshare about their financial life? I met a friend for drinks, and he brought along another friend who had just landed a really great job. I know this because she wouldn't stop talking about it, down to the details of exactly how much she was going to make and what her stock options would be worth."
In the Facebook age, privacy is sometimes seen as old-fashioned. Some people regularly share every boring, sordid or embarrassing detail of their lives.
But oversharing about money can be particularly disconcerting, because it turns what should be a social interaction -- getting to know someone new -- into a potentially competitive game of "how much are you worth?"
"Maybe they're just excited or clueless -- well, this one is definitely clueless -- but I don't think they're thinking about the other people," Post said. "Getting into the specifics [of how much you earn] makes the conversation about money instead of about you."
Faced with such oversharing, Post would change the subject. A good approach might be to ask the oversharer what her job duties will be, or take the conversation in a totally different direction by asking where she grew up or what she likes to do in her spare time.
"[What do you do] when someone wants to give you a large gift and you feel it's too much. For instance, my brother-in-law has had a really profitable year this year, and feels that he has to 'make up' for the years that he couldn't really do Christmas. Now he wants to buy us something in the several hundred dollars range."
This brother-in-law thinks he's being generous. He may not be fully aware that he's playing the big shot -- and potentially making others uncomfortable.
A similar situation can develop when a more affluent person constantly wants to pay the way for her friend who is less well-off. A more thoughtful approach might be to engage in activities that both can afford. Healthy adult relationships are based on reciprocity, after all, not handouts.
"I think you can say, 'please do not do that,'" Post said. "'I appreciate the sentiment, but that would make me uncomfortable.' "
Rather than put your brother-in-law on the spot, make this about your feelings, said Post. You can follow up with an assurance that there's no need to "make up" for the past.
"What you can say is, 'I like our relationship the way it is,'" Post said.
More from Liz Weston:
Liz Weston is the Web's most-read personal-finance writer. She is the author of several books, most recently "The 10 Commandments of Money: Survive and Thrive in the New Economy" (find it on Bing). Weston's award-winning columns appear every Monday and Thursday, exclusively on MSN Money. Join the conversation and send in your financial questions on Liz Weston's Facebook fan page.
