How should Muslims treat Jews and Christians?

The Quran calls them "People of the Book", i.e., those who received Divine scriptures before Muhammad (P). Muslims are told to treat them with respect and justice and do not fight with them unless they initiate hostilities or ridicule their faith. The Muslims ultimate hope is that they all will join them in worshipping one God and submit to His will.

"Say (O Muhammad): O people of the Book (Jews and Christians) come to an agreement between us and you, that we shall worship none but Allah, and that we shall take no partners with Him, and none of us shall take others for Lords beside Allah. And if they turn away, then say: Bear witness that we are those who have surrendered (unto Him)." (Quran 3:64)

What about Hindus, Bahai, Buddhists and members of other religions?
They should also be treated with love, respect, and understanding to make them recipients of Invitations to Islam.