I have been to India a number of times. Among some basic tips I would recommend ;
Getting your shots.
Taking your anti malarials if needed where you are intending visiting. Some parts of India do not have the mosquitos that carry malaria, check online.
Staying at the best accomodation that you can afford.
Eating vegetarian food only unless you eat in posh hotels.
If drinking water, drink only bottled.
Having said all that...relax ! Enjoy ! India is wonderful and chaotic, leave all your expectations behind and open to the experience..