early morning = madrugada (Midnight to 6:00 am)
morning = manhã (6:00 am to Noon)
noon (midday) = meio-dia
afternoon = tarde (Noon to 6:00 pm)
evening = noite (tardinha, noite)
night = noite (6:00 pm to Midnight)
midnight = meia-noite

Appropriate Greetings
good morning = bom dia (Midnight to Noon)
good afternoon = boa tarde (Noon to 6:00 pm)
good evening = boa noite (6:00 pm to Midnight)
good night = boa noite (6:00 pm to Midnight)

Hello = Olá!
Hi = Oi!
How are you? = Como vai?
How are you? = Tudo bem?