You can travel from India to Bhutan by air or by train or by rod,
1. You can go by Air. Bhutan Airlines and other private operators operate flights from Delhi, Kolkata, Mumbai and Guwahati and other important airports in India to Paro. You can refer to the sites of various service providers and decide on the service based on the cost of the ticket on the day of your journey.
2. You can go to Hasimara, the nearest station in India, to Bhutan by train. Trains to Hasimara are available from important railway stations like Kolkata, Delhi etc. in India. Alternatively, you can travel to New Jalpaiguri by train. From both the places you can go to Bhutan by hiring a taxi. The town which is near to these two stations is Phuentsholing in Bhutan.
3. By road also you can go. That depends on the place from where you are starting. Taxi services are available from the nearest places in India to Bhutan. As Bhutan is very near to West Bengal you can hire a taxi from many places in this state and reach Bhutan.
No Visa is required. But a permit is required. This permit can be obtained on arrival from the Immigration Office in Phuentsholing. Permits will be issued at Paro international airport for the people travelling by air. You have to carry identification proof like Voter Card, Aadhar Card, or passport A passport size photograph, a self-declaration letter and a hotel booking letter are required for getting the permit. Based on the places you are going to visit you may require a special permit also. You will get the full information from the immigration office and they will advise you based on your itinerary.
The duration of the journey will depend on the places you want to visit. When I visited this place, I spent about 8 days and I obtained a permit and special permit also. You can plan based on your plan.
The following are some of the luxury hotels in Bhutan. You can visit their websites and reserve your rooms.
1.Hotel Le Meridien Thimphu.
Chorten Lam, P.O. Box 01286 · Thimphu, 01286 Thimphu, Bhutan, There is a facility for picking up from the airport. You can ask for it when you book the room.
2. Resort Le Meridien Paro Riverfront.
P.O. Box # 1265 Shaba, Paro, Kingdom of Bhutan, 1265 Paro, Bhutan. Airport pickup is available.
3. Resort Taj Tashi Bhutan
Post Box No 524, Samten Lam Chubachu, 11001 Thimphu, Bhutan . Airport pickup is available.
4. The Postcard Dewa, Thimphu, Bhutan
Neyzerkha, Khasdrapchu, 11003 Thimphu, Bhutan
5. Hotel The Pema by Realm
Melong Lam Lower Motithang, 11001 Thimphu, Bhutan.
There are many others and you can select based on your budget by visiting various tourists sites or the sites of the hotels.