You can catch bus from state bus depot. but last November we had opted State transport bus upto Kathgodam, very tidious journey it was. better if you can book 2x2 seat in luxury bus from a local travel agency.
Hi bidyut, travel from nainital to hrishikesh is very tiresome and there are a lot of local HP toursim buses from nainital to hrishikesh. Nainital is aprroximately 250 kms from hrishikesh. But as per my advice, it will be better if you are able to book a volvo or atleast a 2×2 express for a comfortable journey. Train is also an option but for that you will have to travel to kathgodam which is approximately 20 kms from nainital. Hope this helps you.