-Be it's own dedicated room. This is the biggest thing. If it's just a living room then it's a "media room".
-Have a good quality, widescreen, HD display of over 50". Most likely in a dedicated room a front projector will be used, however I think plasmas (I guess LCD's too) of a larger size can be used in smaller rooms.
-If a front projector is used, a good quality screen must be present. Not screen goo or any of that junk.
-Have a good quality DVD player for watching standard definition movies.
-Have an HD broadcast source such as cable, satellite, or OTA.
-Have some sort of lighting control.
-Be fully automated and have some sort of automation/integration system.
-Have a dedicated home theater receiver of good quality.
-In most cases, have amplifiers (not the receiver) powering the speakers.
-Feature at least 5 speakers of good quality. They must all have at least one 4" driver or larger, and a tweeter. They all must be matched and generally should not be paper.
-Have at least one powered subwoofer designed to match the speakers.
