Contact the producers of the film to see if DVD rights are available. If you are unsure of who that may be, the Internet Movie Database (www.IMDb.com) will have that information listed for most films, both completed and still in production.
Begin negotiating an offer if rights are still available. The price will depend on factors including the film's budget and production costs, marketability and any other offers on the table.
Work out the terms of the deal, which will include the territory (domestic and/or foreign rights) and the length of time, which can be for a period of years or in perpetuity.
Ensure that the film has all the necessary rights and clearances secured for distribution, including any music used in the film and any life rights to people in the film if it is non-fiction.
Have an attorney draw up the contracts, or visit a site such as www.perfectlylegalforms.com, which has forms for film rights available for purchase.
Map out a strategy for getting the DVD into stores once the rights are secured.
If the DVD rights to the film are already held by another entity, check to see if those rights will expire at any point in time, and follow the same steps to obtain the rights once the current deal expires.