Slow down to greet someone you know. You don't have to stop what you are doing (walking, working, shopping).
Greetings in Passing
It is polite to greet a person you know. However, you don't always have time to stop and have a conversation. Just remember to smile as you say hello. A small wave is also polite. Sometimes you pass the same person a second time on the same day. You can say "hello again" or just smile.
Say an appropriate form of hello.
Smile and wave.
How's it goin'?**
*Good night is a farewell(goodbye) phrase. It is NOT a greeting to use at night time.
**Native speakers often shorten "going" to "goin" in casual greetings.
Slang greetings in passing
Using slangin a greeting is typicalbetween close friends. Teens often use slang when they greet each other. Certain English speaking countries also have their own popular form of "hello".