If passing it to someone else, try to avoid touching it, and always use your right hand to pass a plate. In country places try to avoid putting used dishes near clean ones. Men should avoid physical contact with women. Even shaking hands is regarded as rather forward. A traditional Indian greeting is much to be preferred.
Conversations can be surprising.
You will often be asked what appear to be rather impertinent questions about your financial or family circumstances. These are not meant to be rude. Don't forget that Indians reveal a lot about themselves to each other simply by their names and the way they dress. You don't automatically give that information, and if people are interested they will ask. V.S. Naipaul, India, a Million Mutinies Now , Minerva, 1990.