Different Ways to say "Hello"

Sometimes you want to be different and don't want to repeat hello or hi all the time.  Why don't you change your "hello's" using:

- howdy!

-  Hey!

- What's up!

- Long time no see!

- It's good to see you!

- Good day!

- Yo! (very informal)

Not necessarily  expecting an answer:
- What't going on?
- How are you doing?
- How are you?
- how have you been?

Formal greetings, depending the time of the day:
- Good morning
- Good afternoon
- Good evening