Let everyone go ahead of you. Whether you are driving, waiting to use the copy machine at work, getting into line at the supermarket, or leaving a restaurant at lunchtime, let everyone you encounter go in front of or get served before you.
Drive as if everyone else has the right of way. Stop for pedestrians. Let people change lanes in front of you without difficulty. When the deli man barks, "Who's next?" point to the person beside you and say, with a smile, "He is."
Make sure you let these people know that you're deliberately deferring to them. Don't pretend you're just being indecisive or weak, but rather that your sense of courtesy is so refined that you look for opportunities to exercise it. In most cases, you don't even have to say anything. Use hand gestures to allow people ahead of you, and watch for their reactions.
— Alan Epstein in How to Be Happier Day by Day