An etiquette conundrum to end all etiquette conundrums.

By Betsy Cribb
""Tips"" jar on coffee shop table
Credit: SDI Productions/Getty Images

If Mama (or Emily Post) taught you to mind your Ps and Qs, you know that you're supposed to tip wait staff at a sit-down restaurant between 15 and 20 percent. Tipping is a tangible way to thank your waiter or waitress for their time and service. Most of us know the drill and compensate our waiters accordingly. But just because you know better doesn't mean your dining companions do. Tipping can be a particularly tricky subject to broach, especially as etiquette dictates that money is never a topic of polite conversation. While you can't—and shouldn't—force anyone to tip, there are a few subtle ways to encourage penny pinchers to pony up.

Drop Hints

Because I avoid confrontation like the plague and instant grits, I like to drop hints about appropriate tipping by talking through my calculations when the check comes. "My dad taught me this easy trick that helps me so much with tipping: Give $2 for every $10—that's a 20 percent tip. And this check is $15, so that means I should leave $3. Works every time!" Sure, you have to act like a know-it-all to pull this one off, but at least you're making known your stance on what constitutes an appropriate tip without directly calling anyone out. If conflict makes you want to crawl into a hole, performing mental math aloud is a decidedly painless alternative.

Tell a Story

As you're waiting on the check, channel Aesop and share a fable that ends with a tip on tipping. Maybe you once ran out of cash and could only leave behind a 10 percent tip: "I felt horrible and ended up running to the ATM down the street to get a few more dollars to bring back to the waiter!" Or perhaps you had a friend who unintentionally tipped 200 percent once: "We still laugh about it. You can never be too generous, of course, but Lucy Wade knows now that a 20 percent tip is perfectly appropriate." Deliver your little tipping tale with enough levity, and your lowballing friend will never suspect you're aiming your anecdote directly at her.

Pick Up the Slack

If you don't have the time or energy to school your dining companion in tipping etiquette (or you don't know him well enough to say something), tack a little extra onto your own check (or discreetly leave cash on the table after he's left) to compensate for his stingy tip. While this method is certainly appreciated by your server, who won't get short-changed by Scrooge, it's not exactly sustainable—especially if you're with a friend you dine with often. Additionally, that friend will be left to his own impolite devices if he's not out with a friend as thoughtful or generous as you are, and who will spring for the extra tip then?

Stick to Activities that Won't Require a Tip

If your friend just hasn't gotten the hint or won't change her low-tipping ways, it may be time to start kindly declining invitations to dine out with her and suggest other ways for you to spend time together instead: A trip to the movies won't require her to tip anyone … just don't be surprised when she eats all the popcorn you paid for.

WATCH: 5 Things Polite People Always Say

If you've ever been to Chick-fil-A, you know the power of a couple nice words. At that beacon of chicken sandwich goodness, there's no "sure," "I guess," or "yeah," in earshot; to just about everything, the employees say, "My pleasure." But whether you work at Chick-fil-A or not, there are a few phrases you can incorporate into your daily vocabulary to sound particularly polite. Watch the video above to find out what they are.