When you plug in your new HDTV, everything won't magically turn into high-definition. Here's what to do:
Check the receiver's display settings menu and make sure it's set to output 1080i.
Not all digital programming is high-def; some is still standard-def. You must tell the service provider that you want high-def, and in some cases, pay for that tier of programming. (A cable connected directly to your HDTV might get you HD for the major broadcast channels, without a box and HD service, thanks to your TV's QAM tuner. You can also get free off-air HD with a good antenna in many areas.)
Connect the box to your TV's component-video or HDMI input. Other inputs can't provide HD. Use HDMI if possible. It carries audio and video on one cable, versus five for component-video and an audio pair. You must use HDMI to transmit 1080p and upconverted DVD video from Blu-ray players.
The HD version of a channel has a different number from its standard-def counterpart and usually has the letters HD in the listing.
Most new TVs will ask you to choose "home" or "store display" settings when you first power up. Go with "home." Store settings usually look garish in home lighting. Then press the menu button on the remote to access the video or picture menu, which lists various picture modes. Cinema, Pro, or Standard (names vary by brand) is usually a much better choice than Vivid or Dynamic. As you switch modes, settings for brightness, color, sharpness, and other attributes change. See which you prefer. Also, set the color temperature to "Warm" for the most cinematic look.
To adjust settings individually, choose the Custom or User mode. Freeze on a DVD or DVR image with people and a mix of dark and light areas. Adjust brightness and contrast, then color. A good practice is to set attributes to a middle or neutral position and adjust up or down until the image looks realistic. Generally, high settings for color and brightness look unnatural. It's usually best to turn off noise reduction and set sharpness at a minimum so that details don't look harsh and overly enhanced. After fine-tuning, detail in dark and bright areas should be visible, and colors (especially skin tones) should look lifelike.