Sat Sri Akal is the standard Sikh greeting and is used across Punjab by people of every religion in ordinary conversation. It is a truncation of a longer form and means, roughly, true is the timeless one.
Waheguru ji ka Khalsa, Waheguru ji ki Fateh is the formal Sikh greeting given by Guru Gobind Singh Ji, and is used at gurdwaras and on formal occasions. The response is the same words.
Salaam and Assalam-o-alaikum among Muslims. Ram Ram and Jai Mata Di in Hindu households, and Ram Ram is also a general rural greeting in the eastern districts.
Fateh bulao, call the fateh, is what a Sikh gathering is told before it disperses.
The greeting a person uses places them within a sentence, and the fact that Sat Sri Akal has become general across communities in Indian Punjab is a piece of social history in three words.
In Pakistani Punjab, Sat Sri Akal has largely gone out of general use since 1947, which is the same piece of history running the other way.
The greeting is given first by the person arriving and answered by the person already there, and among Sikhs it is given standing. The order is not negotiable and getting it wrong is noticed.
Rab Rakha at parting, and the older forms among Punjabi Hindus and Muslims, mark the community without anybody having to state it.
The greeting is also a question. Ki haal hai, and the expected answer, are a whole exchange about the family, the crop and the health of the animals, compressed into a few seconds.