I haven't dealt with bootlegs in a while, but it used to be pretty easy to detect. Since most of the time you're getting a bootleg is a title not available in your country, look to see if the region coding is right. Like, it'll say "Region 3" on the disc, but play just fine in a Region 1 player. Also look to see if there's missing content. Extras, mostly. Or it will claim to have DTS, but there's no DTS actually there.
CINEMA PAFF - Your BB-Movie Showcase *
* - The extra B is for BYOBB