How to say "Hello" and "Goodbye"?

To start conversation say:

• "Hi!" or "Hey!"
• "Hello!" or "Well hello!" 
• "Good morning" or "Morning!"
• "Good afternoon" or "Good evening"
• "How are you?"
• "What's happening?" - "Not much." 
• "How's it going?"- "Not bad."
• "What's up?" or "Wazzup?" - "The usual." or "Nothing much"
• "S'up?" - doesn't need to be answered
• "What's up?" - "Pretty good."

To end the conversation say:

• "I've got to be going."
• "It's time I made a move."
• "I really must be running along."  
• "Is that the time? I've got to go."
• "It's time I left."
• "I've got to get back to... home/college."

To say goodbye use:

• "See you later."     
• "Catch you later."
• "Take care."
• "Ta-ta" or "Ta-ra"
•  "Cheerio" or "Ciao"