So things to prepare for NOW - you're going to a very hot, very poor country. It is very dependent on where you'll be what you need to bring with you. Medically, get all your prescriptions filled for that time being. You can find them in India cheaply usually, but sometimes it can be difficult as a new foreigner. As someone who lives in a region that doesn't have high malaria rates, realize you may be at risk to get malaria, and no it's not fun to get the meds. And also there's an entire country here that don't take those meds. Anyway, IF you decide to take them, get the ones you take once a week. Go to the doc and get all your shots, a tetanus booster, and a rabies shot (you never know and they last for some time).
Figure out banking - it's easy to use Western Union to transfer money but if you can, find a bank like mine - doesn't charge any conversion fees, nor foreign transaction fees, nor other ATM fees. Message me if you want my small local bank which is a miracle worker for foreign travel. Get someone to help you figure out banking in India. It's a pain in the butt, and India controls money movement, among other things, much more heavily than the US does.
If you have size 9 feet or bigger, bring good shoes. You'll eventually find somewhere that has size 9 shoes. You can also buy online. Bras are also something that I would suggest you bring. It will save you any embarrassment.
Even if you're in a big city, bring clothes that cover you. People will always stare. Hawkers are a nightmare up north - don't even bother being nice to them when they're pushy!
Food - well you'll get used to it or find something you like! There's lots! If you're ever in the south, dosa(i) and idly (idlli) are delicious and not very spicy.
The actual biggest thing I would say is that after you land, find someone who speaks the local language, get them near where ever it is you live, and make certain they help you find the closest chicken, beef, pork, and fish butchers, the local veggie and fruit market, and the regular store. Make certain they tell you prices of lots of things so that you know that you're not being ripped off. The prices do fluctuate, but you'll have a better grasp. Better yet, get them to tell the local shop person that if they give you a good price, you'll always go to them. Saves you having to be worried about being ripped off.
Buy a pressure cooker (in India) - you will need it to cook fresh beef especially. This is because in the US they let beef hang for like 10 days and here it was killed that morning, so the meat is tough. Also it will help you cook lentils which are a huge ingredient in lots of Indian cooking.
Learn to cook local dishes. It will save you TONS of money and TONS of time going back and forth to the big grocery store to buy western products. Oil, milk, salt, sugar, flour - these all come in plastic pouches, so you need containers in your kitchen to hold them.
I have like a million and one more things to add to this, but NO TIME! Talk later.