(FORTUNE Magazine) – Sometimes the stickiest business situations occur outside the office. What, for instance, should you do if your boss accidentally takes your roll at dinner? To answer this and other pressing etiquette questions, FORTUNE caught up with social graces guru Margery Sinclair. A former model who devoured her first etiquette book at age 12, she now teaches the seminar "Good Manners Are Good Business" at the Academy of Financial Service Studies in Milwaukee and travels around the country to instruct executives from companies like Zurich Scudder and MetLife in business-dinner comportment.

Q: Why are good manners so important in the business world?

A: These days employees are often just handed an AmEx card and told, "Here, go and entertain the clients!" Many of these people have been eating pizza since college and are really in trouble.

Q: Settle the debate: To advance our careers, should we be cutting and switching our utensils American-style, or submitting to European cutlery use?

A: The further up in management you go, you're going to see more people eating European-style. It's much more practical and sophisticated than cutting and switching. I eat European.

Q: It seems like a lot of etiquette disasters occur around the bread plate.

A: It's very common that people forget the "liquids on the right, solids on the left" rule and steal their neighbor's roll. As with all etiquette matters, the point is to avoid embarrassing other people. It is acceptable to find the double roll and ask for that to be passed--or if it's your boss, you might just look at the big picture and go without. But always remember--butter just one bite at a time.

Q: What should you do with your napkin if you get up from the table mid-meal?

A: Place it on the seat of the chair. This is a case where it's much easier to remember the reason rather than just a rule. Chances are the napkin has food or lipstick stains on it, and you don't want others to have to look at your dirty linen.

Q: Can anything be done about people who talk with their mouths full of food?

A: My advice to everyone is this: Eat a sandwich in front of a mirror. Most of us don't realize what we look like when we're eating, but this is what someone sees when they have lunch with you.

Q: Anything else one should definitely avoid doing at the dinner table?

A: In a social situation I once watched a 50-year-old CEO break a roll that sprayed crumbs all over. When this happens one should just ignore it, but he proceeded to repeatedly lick his index finger and transport the crumbs into his mouth.

Q: So as an etiquette expert, couldn't you call him on it?

A: That's the thing: Unless you're there as a teacher, it's bad manners to correct other people's bad manners.