Check the release date of any DVD available from non-traditional sellers. Legitimate stores will not sell a DVD until the studio release date. Pirates will often try to beat that date to get a jump on legitimate stores. Check official release dates at the website of the film or TV show, or amazon.com.
Check the case for holograms. Many legitimate companies stick a logo in a holographic sticker somewhere on the outside of the case. These reflective silver stickers are expensive to make, and few pirated DVDs will have them.
Check the condition of the front and back covers of the DVD. All of the photographs should look sharp. The text should have no spelling mistakes. A DVD with a homemade cover is likely a fake or copy.
Open the case itself and check its quality. Cheap casing is one way pirates make money off DVDs. The case should be in good shape, and should not have any leaflets on the inside advertising products other than those endorsed by the movie company.
Check the look of the disc for any imperfections. Many pirate DVDs will have either no picture on the top side of the disc, or the picture will be off-center, blurred or incomplete. The underside of the disc must be silver. Other colors may play, but the industry uses silver discs for its first-run DVDs.
Picture and sound quality are two other ways to tell a DVD is a pirated copy, but you can only check those after you buy one. The worst are those filmed in a movie theater where shadows and people moving around in the foreground show up in the picture. Any DVD you buy with those problems should be returned immediately.