To truly do justice with your HD TV, you will probably need to bring both colour and contrast down from the factory settings. With sharpness honed, the detail will leap at you, particularly on Blu-rays and HDTV broadcasts.
It is important to make your adjustments with the room environment as it is when you are watching TV. So if you draw the curtains, do so for calibrating your picture as well.
However, no amount of fiddling will make a difference if your TV is in the wrong position to begin with. Get a TV wall mount and put your TV at the optimum height and angle for the best viewing experience.