Salutations

hej 'hello'
morn [informal greeting]
god dag 'hello; how do you do'
god morgen 'good morning' (not used after 10:00)
god aften 'good evening' (used late day, early evening after which:)
god kveld 'good evening'
god natt 'good night'
God natt, og sov godt. 'Good night and sleep well.'

god reise 'have a good trip'
ha det (bra / godt) 'goodbye'
morna 'bye bye'
adjø 'goodbye' (very formal)
på gjensyn 'looking forward to seeing you again'
'Hello' is used on the telephone.

How are you?

Hvordan har du det? / Hvordan går det? 'How are you?'
Takk, bare bra 'Just fine, thank you'.
Takk, fint. 'Fine, thank you.'

Thank you

Mange takk. 'Many thanks'
Tusen takk. 'Many thanks' (lit. 'a thousand thanks')

Takk for maten. (Used after a meal.) Velbekomme 'don't mention it'

Takk for i dage / aften 'Thanks for this afternoon/evening'.

[The day after:] Takk for i går. 'Thanks for yesterday.' (used more often than in English)

Takk for meg 'Thanks for having me'

Takk for sist 'Thank you for last time' (used more often than in English)

Det var en veldig hyggelig aften. 'That was a very nice evening.'

Greetings on special occasions

Gratulerer med dagen! 'Happy birthday!'

God Jul og Godt Nyttår 'Merry Christmas and a Happy New Year'
Alle gode ønsker for julen og de Nye Året. 'All good wishes for Christmas and the New Year.'
Godt nyttår og takk for det gamle! 'Happy New Year and thanks for everything last year!'
Jeg håper du får et godt nytt år! 'I hope you have a happy New Year!'

Misc

Unnskyld 'Excuse me'

Vær så god. 'Here you are'; 'May I help you' (when answering the phone) 'Vær så god' can also be used to give permission for a request: Ja, vær så god. 'Yes, do carry on.'