One must possess a passport which is valid for minimum 6 months from the date of entry into India. Many countries have been included in the list of countries whose citizens are provided E-Visa facility provided they apply 72 hours in advance. Other nationals need to obtain an Indian visa in advance to enter India.
There is no need of any vaccination except for travelers coming from Africa, South America need yellow fever vaccinations.
It depends on which part of India if you wish to visit. In case you are interested in visiting Ladakh or other parts of Himalaya then summer season is the best time. If you want to visit Rajasthan, other parts of North India or South India then winter season ( October till March ) is ideal period. Even traveling during monsoon months (July – September) is also not a bad idea to visit Rajasthan and other places it presents a good tourism opportunity during this time as one can stay at Luxury or Palace hotels without spending a fortune during those months.
The best way to travel within India is to travel by road as this offers you an opportunity to have a glimpse of real INDIA as you can visit en-route villages and small forts at your own pace which is not possible by air or by train. But, if you are traveling to long distance, then taking a flight or trains can be more convenient and to save time.
Yes. It is advisable that you buy a comprehensive medical / travel insurance in advance from your country before traveling to India.