Chosen Islamic Manners

'Do not greet the Jews and Christians with Salam. If you meet any of them in a path, force them to walk on the side.' (Muslim)
If one wants to greet them, let him greet them with a greeting other than the Salam.

If the non-Muslim greets the Muslim with Salam but it is not clear what they actually said, one should respond by saying: 'Wa alaikum'. But if it is audible and clear, then one can respond appropriately.

There is no sin if one asks them about their health, their family and children, as is mentioned by Sheik al-Islam b. Taymiyyayh, may Allah have mercy on him.