Bollywood is the collective term used to describe the film industry in India. While most Bollywood movies are still made in the Hindi native language, the trend of English-language movies is on the rise. Most Bollywood movies are formulaic, with the same themes running through the stories. They are almost all musicals and tend to run 3 hours or longer. A deep understanding of Indian culture and history is required to become a scriptwriter for Bollywood.
Immerse yourself in Indian culture and history if you are not a native Indian. Talk to friends that were born and raised in India to get an understanding of the social and political influences they grew up with. The more you can know about the customs and habits of the Indian people the better chance you will have writing an Indian film script.
Learn the Hindi language. Although many Bollywood films are now partially presented in English, the scripts must still be written in Hindi or have Hindi translations for English included.
Study as many of the Bollywood films as you can find on DVD, VHS or other medium (see Resources below). Since Hindi films have reoccurring themes, such as lost love or revenge, you will need to see how these themes are executed on the screen. Hindi films also tend to be more melodramatic than Hollywood films.
Write your script bearing in mind that Bollywood movies tend to be at least twice as long as American films. A 3-hour movie with an intermission is what you should be shooting for when writing your script. Almost all Hindi movies are musicals, so be sure and include song and dance.
Submit your finished script to any one of the many companies producing scripts for Bollywood. Dharma Productions and Sanjay Leela Bhansali Productions are two companies to start with (see Resources below). You can find other companies by looking at the credits on the DVDs you watch.