The Prolost blog's post Your New TV Ruins Movies is over a year old but still packed with relevant information on why shopping for a new TV is difficult in a busy store as well as the settings that environment requires and how it affects your experience when you take it home:
Maybe you got a new TV for Christmas. Or maybe you just got one recently. Maybe you are thinking of buying one. Whichever is the case, take heed: your TV will try very, very hard to make whatever movies you watch on it look not just bad, but aggressively, satanically, puppy-drowningly bad.
It features a handy guide to turning down the brightness and moving your TV into at least a general "movie mode" as well as how to turn off the motion smoothing that can ruin lots of TV and almost all movies.
I always do two things when buying a new TV: one is going through the options to make sure automatic stuff like motion smoothing is turned off, and the other thing I do is Google search the phrase "cnet reviews calibration tv [model number]". Cnet reviews consistently has the newest reviews and part of every TV review is how to calibrate your TV to match their optimal settings. They include every single option screen's settings and it frequently takes me about 20 minutes to complete but it is worth the effort and I'm always rewarded with a really high quality picture.