Greeting people in Islam is a very encouraged practice by the Prophet of Allah 
. One greets with the following words:
May peace be upon you
The person receiving the greetings should reply:
Wa alaikum salaam
And upon you be peace
- Narrated from Abdullah ibn 'Umar  that a man asked the Messenger of Allah : "What is the best thing in Islam?" He said, "Feeding others and giving the greeting of salaam to those whom you know and those whom you do not know"