I would like to know if we can tip our guides in US dollars or does it have to be INR?

rubies or emeralds only.

Use rupees and be prepared to hear them ask for more. My advice is to tip them and then just walk away.

Always give rupees, so that your guide doesn't have to go to an exchange. I usually get an envelope from the hotel front desk the night before, and then I put the tip in the envelope, shake hands with the guide, and disappear into the airport. In India, all of our guides were gracious and did not ask for more money.

Good idea. Put money in a sealed envelope and leave before they can look into it. We always gave open amounts of cash. .

http://timesofindia.indiatimes.com/b...w/45755289.cms

This may help.