I highly suggest Himachal Pradesh state. Dharamsala (or rather mcleod ganj) where the dalai lama lives is really really nice and quite a change of atmosphere from india, since its mostly tibetans living there and they are calmer and less intrusive. Also if you're into trekking, Parvati valley, wow! If you head to anywhere around those areas let me know Ill give you some more indepth tips

If you go to Goa, do not, I repeat, do not miss the opportunity to go to Hampi! Its a night bus away from Goa, in the neighbouring Karnataka state, and an amazing place!!! Just check google images and you'll see a bit. Ask jbark, he's been there too!

Goa is very nice, laid back beach life, rent a bike/scooter and just drive around, awesome feeling of freedom. Careful with the police specially around christmas/new years time. There are a lot of fake clique hippies but also some very nice people to meet. Dont stay in mainstream-tourist beaches like bhaga, rather go for Anjuna or Arambol. Also do visit the german bakery in anjuna, it has wonderful food and a very cool laidback atmosphere, awesome place to hang around.

I suggest if you go all the way to India, though, dont only stay in Goa, do travel around some more. Theres a billion more things to say but all leave it at this for now