Best way of saying Goodbye Hello

Great opportunity to have students practicing how to say "hi" and "goodbye". Have them using different vocabulary:

Saying "hi": Hello/Good morning/ Hoe do you do?
Saying "goodbye": I'll see you later/ tomorrow/ bye bye/ It's been a pleasure talking to you...

Another interesting thing about the subject: opposites!

Hello=goodbye/ good morning=good evening/ good=bad/ soon=late...