Each term, I give a lecture to graduating students about basic business etiquette. It's one of those things you presume everyone knows and then another designers tells you, "I had lunch with one of your recent graduates. He ate the food like a cat with his face in the plate."
This is, of course, a rare instance, but it can't hurt to refresh the point that eating like a cat is distasteful and embarrassing. The students laugh and watch me as if I were explaining how to do basic math to astrophysicists. But when I pass out the plastic forks and knives and demonstrate the right way to hold them, the room falls silent. I'm amazed how many people at fine restaurants or dinner parties hold their knife and fork as if they were killing a mammoth. It isn't going to try to get away. There is no need to hold it down with a fork and clenched fist, then stab at it repeatedly.
I also remind them of basic business etiquette. Stand up when someone enters the room. Don't sit there silently staring at your lap. Shake hands firmly, not as if your were holding a perfume scented handkerchief to your nose. Open the door for others. Don't chew gum at work. And don't ever, ever say to anyone, "You don't remember me do you?" It's best to remind them, "My name is Sean, we met previously at Joan's club. You were Betty's bridge partner that evening."
Some of these rules may be outdated, but will never be wrong. It's better to err on the side of good manners than being too casual. And if any of the students at least remember that a place setting is BMW (left to right: bread, meal, water), they won't steal my water glass at lunch.