I have always wanted to go visit India, and I might actually get the chance in the next year or two. What should I know before I go? What should I do when I get there?
What should I eat???
I found India a bit of a headfuck, even though I’d spent a lot of time in east Asia beforehand. Despite this, I am glad I went, and once I got out of Delhi things went uphill rapidly.
Read up on the religion, as it’s a huge part of daily life. Also read the history of the place - it’s vast, but there’s some fantastic fictionalised history that will give you the story in an entertaining form:
A Suitable Boy - Vikram Seth (long! Deals with independence)
Midnight’s Children - Salman Rushdie (poetic! Deals with post-independence)
A Fine Balance - Rohinton Mistry (tragic! Deals with Indira Gandhi’s “emergency” in the 1970s)
For non-fiction, try India: A Million Mutinies Now - V.S. Naipal (heavy! Deals with India in the 1980s)
What you should know? I don’t know, but these are my experiences in brief:
It’s ridiculously crowded around Delhi (and I’ve heard Calcutta is worse, though I’ve never been there). There are so many people everywhere it’s almost impossible to conceive.
Expect to see some of the most soul-wrenching poverty you can imagine.
Realise that it’s going to take a couple of weeks to get used to, and be prepared to be a bit freaked out at first - it will pass.
Many people you meet are trying to sell stuff, but using their charming personality to do so. This can make you a trifle mistrustful.
The standard of driving is probably the worst in the world.
Drink only bottled water. Don’t open your mouth in the shower.
People don’t line up very well - most things where you have to join a crowd to get a service, like at a train station or bank, is a non-violent riot.
Eat? The most amazing curries ever! Dhosas are great too, and pakora, and bhajia, and papad masala. Mmmm. Most of the food I had there was fantastic.
Avoid salads unless the restaurant washes it in sterilized water.
Hope you get there!
And BTW the correct phrase is not “what do I do?” but “what to do?” 
Read my website at http://www.jenniferrobot.com. It’s got lots of experiences, pictures, and a rudimentary guide to what you’ll need to do on a practical level to prepare. The Wikipedia Travel pages on India are also very good. So is the background material provided in the Lonely Planet (which IMHO is a better guide than the Rough Guide, though the Rough Guide’s “suggested reading” section is very good.) There is a lot of really good information that a lot of people miss in the budget travel guide books.
The Culture Shock- India guide is also really a must-read. It will explain a lot of things about culture that you will see over and over again and might not ever understand on your own.
I’ve had a lot of luck finding good reading about India in the at my local public library- much better luck than nearby bookstores, in fact.
People’s reactions to India vary from “It’s the most amazing place on earth” to “It’s hell on Earth”, so make sure you get a flexible plane ticket. No matter what you feel about it, it will be a strong feeling. It can be a difficult place to travel, but it can be infinitely rewarding.
As for eating…eat everything! The food is great (although it can be hard to find meat at times). You must try Indian Chinese food- it’s not like our Chinese food and it’s not like Chinese Chinese food- it’s something else. The food served at truck stops (any bus you take will stop at one) is hearty and plentiful. In the South “Hotels” (which are really restaurants) serve “meals” at set times- these are an all-you-can-eat feasts served on a banana leafs for pennies. IMHO these are some of the best meals to be found in India- and the cheapest. McDonald’s is a total trip there- imagine McDonald’s with no beef! Some people are uncomfortable with street food (which is not prepared in the most sanitary conditions) but some of it can be wonderful- my favorites were fried chilis and cucumbers dusted in salt and spices and fresh sugarcane juice. And on the trains, people walk up in down the aisles selling all manner of treats. Then there are the sweet shops where you can buy neat little boxes of sweets- some delicately leafed in silver. And for snacks there are hearty parathas and spicy dosas and my personal favorite, spicy little omelets with bread in the middle. And of course there are the tiny cups of sugary milky tea drank several times a day. MMmmmm!
Wish I’d read the Culture Shock book before I went. Good recommendation, even sven. I defer to you as well about the place, because I know you spent quite a while there.
A couple more things that occurred to me:
The trains are fantastic if you can get in the sleeper carriages (first class). Not so good in “cattle”. But far preferable than buses.
No matter what you do, you will get a little sick. Usually, just a couple of days with diarreah, but sometimes a bit more. The western style doctors there are very competent, but also bring with you some good rehydration salts and Imodium (but only use this if you have to, like going on a 16-hour bus trip), and if you can get them, some general-purpose penicillin-type antibiotics; make sure you read the directions and finish the course!
The red stuff all over the walls is paan spit, a mild narcotic made of some kind of leaves and betel nut - people suck it, it makes them salivate, and they spit, a bit like tobaccy-chawin’ cowboys.
BTW Translucent Daydream, I know I’m being a bit of an ass, but your signature misspells the word “truly”. Normally I wouldn’t comment, but a sig is attached to every single post you make.
I haven’t been to India, but the first thing I’d do is check out both FlyerTalk dot com and the Thorntree forum at Lonely Planet dot com. You’ve gotten two great responses so far here, but you’ll have a much more targeted audience at the sites above.
I’d also start looking at flights (get advice on normal fares at the above sites), and sign up at a site like Travelocity to get alerts when prices go down.
Go to a library or bookstore and start reading as much as possible. I usually don’t stop reading about where I’m going until I’m there. You don’t mention how long you would like to be in India for, but you’ll want to decide to just do one city, or multiple cities.
No way you are being an ass! I really appreciate it.
Goes off to edit careless mistake…
See the Taj Mahal. Yes that is a no brainer, but it really is worth it. It is even more beautiful up close.
It is even worse than that. Worse than you can imagine. I think a traffic light is just to indicate which direction is to blow their horn as they approach the intersection. If it is green, don’t bother, if it is red, blow your horn and make sure nothing is coming that is bigger than you are. :eek: And I wish I was exaggerating. 
It is possible to have a hamburger. Not as easy as in the US, but possible. But who really wants one with the foods you will have available. I was too young to appreciate the food when I went. But I would have a lot of fun if I went back now. 
India is a place I have always wanted to visit…that said, my SO has some co-workers who just went to India last month for three weeks…they said traffic was ridiculous, hotels were impossible to book, crowds were beyond belief everywhere and the wife said she would never go back unless she had to…oh, did I mention both of these people were born and raised in India.
Heh. Two weeks after returning from a year and a half in Europe, I couldn’t wait to get out! Heck, I was afraid to ride my bike for a week until I had gotten used to driving around in Poona (which is a nightmare at the best of times).
I always tell friends visiting from abroad to start in Goa. It’s less of a shock than traditional entry points like Bombay or Delhi, and it lets you kinda slowly sink into the India experience, rather than getting thrown straight in the deep end.
get shots
know where your consulate/embassy is
do not go exploring alone
advise from someone who got deathly ill on vacation