I've only spent about a week in India (Delhi, Agra and Jaipur). It was a good trip, but not necessarily 'fun'.
If there is one thing I learnt (as a caucasian), it is that anyone who talks to you on the street (who doesn't have an obvious reason to be there like a shop keeper with merchandise) is probably trying to scam you. Trying to buy a train ticket to Agra from Delhi was a nightmare; we ended up organising a taxi through our hotel. It was hard going from being used to trusting directions and advice from strangers at home, but I got over that pretty quick.
Also, carry plenty of small change; anyone who does absolutely anything at all for you will expect a tip.
If there is one thing I learnt (as a caucasian), it is that anyone who talks to you on the street (who doesn't have an obvious reason to be there like a shop keeper with merchandise) is probably trying to scam you. Trying to buy a train ticket to Agra from Delhi was a nightmare; we ended up organising a taxi through our hotel. It was hard going from being used to trusting directions and advice from strangers at home, but I got over that pretty quick.
Also, carry plenty of small change; anyone who does absolutely anything at all for you will expect a tip.
Have fun :)