Panda, I just went through this process buying my TV and I am very happy with my selection. This post may be long, but it is really everything you need to know in a nutshell.
1. Determine your price range
2. Determine your size TV that fits appropriately in your room
3. Determine which brand TVs with the size you chose fit within your budget
4. LCD vs. Plasma. PLASMA IS BETTER. LCD is more for computer monitors, etc. But for a TV Plasma is better. One major reason is quality of TV picture over time. If you buy a brand new TV that picture always looks beautiful and sharp. With Plasma, they have a useful life over 150,000 hours. Meaning you could leave it on 8 hours a day, every single day for the next 50 years and the picture will look the same as when you bought it. The same cant be said for LCD. You may buy it. Use it for a year, and your picture may begin to go dull.
5. Protect your investment - Manufacturer's warranty will only cover certain things. Warranties from Best Buy and Circuit City cover many other things such as PIXEL LOSS. If your TV starts dropping rows of pixels and isnt keeping that HDTV look, they will try to fix it and if they cant, they will replace it with a brand new one.
6. Protect your investment part 2: Get a Monster Cable or some kind of power surge wall extension outlet.
7. HDMI: This is optional but is for ultimate quality. HDMI = High Definition Multimedia Interface and instead of you connecting the yellow, the white and the red connectors and having 100 different cables back there, HDMI is 1 single cable that connects audio and video in one cable. The cable is sort of like broadband, it sends higher packets of information and fills in your screen for ultimate HDTV quality.
Besides the TV you need to budget for these things and it can nearly double the cost of your TV. Warranty may run you $300, but is a must. Power surge is a must and may run you $125. HDMI is optional and may run you $80, depending on the length of the cable.
TV stand, or a wall mounting bracket is a whole other animal, and will run you another $100+.
As for brands of Plasma: Pioneer is by far and away the highest quality HDTV on the planet right now. But it is overpriced. If you want the best quality of TV picture quality and price, the Panasonic and Samsung are 2 great TVs. The Panasonic isnt cosmetically appealing, with its plain silver look, but it is more of a bargain. Samsung is reasonably priced, has a great picture, and is slick to look at with its black mirror reflective edges.
One more thing, dont be confused with HDTV and EDTV. EDTVC is extreme definition TV and is not as good as HDTV.
Also you want to look at the contrast ratio. This is one of the most prominent stats on the price label at a place like Best Buy. 10,000:1 is outstanding. 5,000:1 is average. As a baseline you can work off that.
My TV is the 32" Samsung HDTV Plasma. 10,000:1 contrast ratio. I got the warranty, power surge, HDMI interface etc.