Excerpted from the India Career Guide

Obtaining a work visa in India is a highly subjective process as Indian immigration law does not specify requirements for a work visa. Often, a company may sponsor a worker to come to India for a job. The most important document is the sponsorship letter from the Indian company, which details the purpose and length of the trop and the financial responsibility of the company. The applicant also needs a valid passport and proof of legal residence in the country where the application is submitted. Work visas are required for spouses intending to start and run their own businesses, consultancy, or internet-based business. Visas are generally valid for one year, and are renewable on a yearly basis.

This is just a sample of what you will find in the complete India guide.