Here's what you need to consider:
How far away will you be sitting from the television? Even though HD delivers a crisp, vivid image quality, it's still not perfect. A television that is too large amplifies every imperfection. While a television that's too small loses the whole "theater experience."
What will you be using your HDTV for? Some technologies deliver truly pure colors while others lose image quality over time. So if you're a movie buff, you'll want a TV that delivers rich colors. If you're a gamer, you'll want a screen you can stare at for long periods of time. And so forth.
Where do you plan on putting your HDTV? If you're looking to mount your HDTV to the wall, you'll want a smaller, thinner HDTV. If you intend on placing it either in an entertainment center or on the floor, it's worth considering a slightly "fuller" model.
Let's talk service. If you want to watch quality HD programming on your HDTV, you'll need an HD service provider. And unlike other service providers, Time Warner Cable gives their digital cable customers basic HD programming FREE. All you need is an HD set-top box and voila!
Looking to become well versed in HD terms, check out our HD Clear & Simple Glossary. 
