The first thing that you need to make sure that is in order is your passport. All visa applicants are required to have one. However, that is not all. Depending on the nationality, the passport needs to remain valid from one to 6 months after your arrival date in Hong Kong. The rules are not the same for everyone as far as the validity of the passport is concerned, which is why we advise that you do the proper research before you are ready to apply for a Hong Kong visa. Also, the passport needs to have at least one blank page.
The next thing on the list is the application form. Unfortunately, a visit to a consulate is required. There are very few nationalities that need to apply for a tourist visa to go to Hong Kong. Other nationalities need to apply if they transit Hong Kong even if they do not plan to leave the airport premises and that requires a trip to an embassy. While there, you will be asked to fill in a form. An alternative would be for you to apply through the HKSAR Immigration Department. You can send the application form and the other required documents, such as photographs via air mail. You can go for the one that you find to be most convenient.
Indian citizens are a particular category of travelers. India is a visa-free country, but all Indians who wish to visit Hong Kong need to apply for a pre-arrival registration. They can do that online, which ultimately makes things a lot easier.
One other thing that you need to meet the requirements for a Hong Kong visa is to present proof of means of subsistence. The immigration officers in Hong Kong need to make sure that you can provide for yourself all the while you are inside the region. It somehow reassures them that you are not there for illegal work.
The last thing on the list is onward or return flight ticket. This is another means of providing reassurance for the Hong Kong immigration that you will not exceed the stay you are allowed according to your visa. After the visa expires, you need to either go back to the country of origin or anywhere else.
All in all, Hong Kong allows most nationalities to visit or transit the region without any other documents apart from the passport, but if you are not from a visa-exempt country, you need to take care of all the issues above. You need to apply for a visa before your trip. That can take up to 4 weeks, so make sure that you have enough time at your disposal for the visa application process.