Greetings and goodbyes

Informal:
Kia ora koe - greeting one person
Kia ora kōrua - hi you two
Kia ora koutou - hi to you and your friends
Kia ora tātou - hi to all of us / the people

Ka kite anō - see you again
Mā te wā - farewell until sometime in the future

Formal:
Tena koe - greeting one person
Tena kōrua - greetings to both of you
Tena koutou - greetings to you and your friends

E noho rā - goodbye to someone staying
Haere rā - goodbye to someone leaving

Can't see:  (On the phone, e-mail)

Hei konā - goodbye (to one I can't see)
Hei konei rā - (to one I can see)