Take all precautions to drink clean water and eat only food that has been properly cooked or heated. Do not display your money or expensive jewellery in public. Watch out for pickpockets and petty thieves. Get used to crowds!
You may need to leave your shoes outside some of the monuments. Photography may be prohibited at monuments, temples, etc. People in India are very religious and some of the traditions have been around for millennia. Respect the culture and their beliefs even though yours may be very different.
