Getting an Indian visa used to entail long queues and large amounts of bureaucracy but the good news is that in recent years it has become a lot easier. The easiest way is through the e-visa programme.
The electronic tourist visa programme is eligible for those travelling for leisure on Hong Kong passports as well as passports from a wide range of other countries including the U.K. and many other western and Asian countries. The Indian consulate in Hong Kong has a list on its website.
The visa is valid only if you are entering India by air, at one of nine airports (Bangalore, Chennai, Cochin, Delhi, Goa, Hyderabad, Kolkata, Mumbai and Trivandrum).
The visa is valid for thirty days from the date of entry.
Your visa needs to have at least six months of validity from the arrival date in India and at least two blank pages. You need to complete and submit the form online here. At the time of applying you need to pay the application fee online. It is US$48 for Hong Kong and most other countries, sometimes subject to a small card service charge on top.
The online requirements were less than I expected and the system though not perfect was decently smooth – my biggest annoyance was that the photograph needs to fall within a narrow range of file size to be accepted, so I needed to save and resave it multiple times to get it to exactly the right file size without reducing the photo resolution too much.
When I applied for an e-visa earlier this year, the application was approved in under twenty four hours. One receives an e-mail confirming acceptance, and should print that out.
At the arrival airport the e-visa channel is clearly marked. I went up to the desk, which had only a couple of people queuing, showed my passport and print out of the e-visa acceptance e-mail, and was promptly given an e-visa stamp in my passport.