Don't call someone more than twice continuously unless it's a really urgent matter and if they don't pick up, wait until they return the call. They might be sleeping, sick, busy, or have something important going on.
If you borrow money from someone, return it, even before they ask for it.
When someone treats you to lunch or dinner, don't buy the most expensive dish on the menu. Also, treat them the next time.
Be nice and kind to waiters, cleaners, helpers, drivers, or anyone offering you a service and treat them with the same respect you'd give a manager or a CEO.
Always open the door for the person coming behind you. It doesn't matter if it is a guy or a girl, senior or junior. You don't grow small by treating someone well in public.
If you take a taxi with a friend, and he/she pays now, you pay next time.
Respect different shades of opinions. Remember what's 6 to you will appear 9 to someone facing you.
Never interrupt people talking. Wait until they finish then say what you want.
If you tease someone, and they don't seem to enjoy it, stop it and never do it again.
Say "thank you" when someone is helping you.
Don't break your promise, or don't make one if you are not sure you can keep it.
When someone tells you a secret, take it with you to your grave, even if you wake up as enemies the next morning.
When someone shows you a photo on their phone, don't swipe left or right. You never know what's next.
Don't fix a time without being punctual yourself. It's a bad habit. Take time management seriously because time is actually money for many people.
Never talk about your riches in the midst of the poor. Similarly, don't talk about your children in the midst of the barrenness.