SOMETHING I STUMBLED ON.

Thought to share this; makes a lot of sense—uncommon social rules:

When playing games with children, let them win.

Compliment the meal when you're a guest in someone's home.

When someone treats you to lunch or dinner, don't order the most expensive dish in the menu. Also, treat them the next time.

Step outside to answer phone calls.

If someone shows you a photo on their phone, don't swipe left or right. If they want to show what's next, they'll do it.

If someone lends you their car, don't return the car empty.