You could use one of the following expressions :

[Hé,] Que y’a ?

What’s up?

Ayez un bon jour

Literally “Have a good day”, used to say “Hello” (became “bonjour”).

Diex vos sait (very formal)/Diex beneï toi

“God bless you”, very ancient, used to start or end a conversation.

You can find more information in « Quelques formules de salutation en ancien français » (Anker Teilgàrd Laugesen, in Revue Romane, Vol. 8, 1973, 1-2).

Bonjour!

There is a possibility that many used the traditional Faire la bise, which means to give a kiss. This is not just the ordinary peck on the cheek, it is the double cheek kiss that we often see on older foreign films. It is a common way for the French to say their goodbyes and greetings. It is in no way used as a romantic display of affection.

I hope this helped!

Merci!