A tourist visa is required for tourists from most countries before arriving in India. The easiest way is to obtain an e-Tourist Visa (also called e-TV, or e-Visa or visa on arrival). You can thus make your request online in advance via the site
If at some point you are no longer able to continue completing your electronic visa application form, you can save your application and come back later to complete the form by clicking on the corresponding button at the bottom of the page.
Once your online application has been completed and accepted, you will have to pay the visa fees (also online payment). Then you will receive your e-visa by email (it is a confirmation with the mention "Granted"), which you will have to print and show when you arrive at the airport in India. Note that you will need at least 3 blank pages in your passport (including 2 face to face).
Once your e-Visa application is submitted, it is possible that a document / image is not appropriate. You will then receive an email to re-download the correct information. Normally you should receive an e-mail within 24 hours after submitting your request if something is wrong.
Your passport should be valid for at least 6 months after your arrival date to India. Visa fees depend on your country of origin, but it's generally 80 US dollars. Your request for an e-Tourist Visa can be made at least 4 days before your arrival in India, and maximum 120 days before. The e-Tourist Visa is valid for 60 days from your arrival in India.
For other types of visas (non-tourist visa or visa longer than 60 days) you should contact the Embassy of India.
Some technical information about the e-visa: the official website of https://indianvisaonline.gov.in/visa/index.html is optimized for Mozilla Firefox, Google Chrome, Internet Explorer (Windows) version 9.0 and above. You should also install Adobe Acrobat Reader version 7.0 or higher on your PC in order to download and print the completed application form. The website is also compatible with Android and IOS devices.