Consumer Reports says:

View TVs critically in the store
TVs are usually set to Vivid or Dynamic mode, which pumps up brightness and color to a level that looks great under fluorescent lights but unnatural in a typical home. In addition, stores often display sports programs, which tend to have super-bright lighting and vivid colors that minimize any flaws in the picture. Ideally, you could ask a salesperson to reset a TV to Normal or Standard mode, but most retailers won't allow this. See if they'll tune in programming with typical indoor scenes (including people, if possible, so you can evaluate skin tones). With an LCD, look at the set from the side, not just head on, to judge the viewing angle. If possible, vary your vertical position too so that you can judge how it looks when you are sitting and standing.

The complete report is here.