Frankly I don't know how to reply to "hey, I want to go to India, what should I do there?" It's a freaking HUGE country, and extremely diverse to boot-- and everyone's taste is different. Besides that, India is absolutely NOT a "casual" tourist destination-- as I'm sure you learned on your first trip, you really have to WANT to go there, so you must have some sort of idea of things you are interested in. What did you like on your first trip, what did you not like? What exactly do you want to do? Be specific:
Temples (which type)?
Archaeological ruins (which type)?
Crazy, hectic pace?
Countryside (ok-- this is most of the country)?
Freaky weird shit (this is in most of the country as well)?
What I'm saying is that you'll have to give us a starting point.