What preparations, if you go to India?

IndiaFriends help advice. I think a trip to India. Talking with people who were there: a variety of reviews - some recommend to go necessarily, the other - just categorically against such a trip.
I know that many yogis were there. So tell us about the main points you need to know a person before a trip to this country: about nutrition, about mobile communications and the Internet, hygiene and sanitation, about transport, about people, prices and so on.
In general, what is ready? something to fear, and what is not?