Be kind to the wait staff at restaurants. Although I have never been a waitress, I have always had tremendous respect for the good ones. They have a difficult job. It's one of the only jobs that utilizes a wide variety of skills. Not only do they have to be informed, have a good memory and be physically fit... they have to do it all with a smile on their face. They are caught in the middle between hurried, overworked cooking staff and the (mostly) self-righteous, arrogant customers they are trying to serve. Tip well. Say please and thank you. Engage them in conversation. Tell them they're doing a great job. Don't allow others at your table to be discourteous or demeaning.
And when something does go wrong, request assistance in a respectful manner. They want you to be happy as much (if not more) than you want to be happy. Be respectful of them and empathetic to the demands of their occupation.
They have a lot on their plate. (Pun intended.)