My parents are from Kerala (southern most part of India) and have been to visit 3 times my whole life. Only thing I can suggest is only drink bottled water. If you're at a restaurant, make sure they break the seal in front of you. I have friends who have been to Goa and I've been told that it's a beautiful place. Sorry but this is all I got. Now if you travel down to Kerala aka God's own country, I may have some more tips.