Have you ever eaten in a foreign restaurant? Did you make any mistakes? Please your experience. Did you learn anything?

I went to the restaurant in Britain in this summer. The dishes all were very delicious. However, I had known there is a system to pay a tip in Britain, but I didn't pay a tip because I didn't know I really should pay it or not. Actually I might have to pay it.
When I was a junior high school student, I went to the restaurant with my friend. (Maybe not a foreign restaurant) I didn't know right how to put a knife and a folk in the middle of eating or after eating then, so my friend taught me it. I thought table manners are so difficult then. I think so even now.