I just recently purchased a 50" plasma tv.  I made my purchase after agonizing over the decision for literally months.  I researched every set, accessed every review site and made the rounds of every "big box" and "warehouse" store and on-line dealer I could find.  I am not a technical whiz.  I do not have any particular expertise when it comes to purchasing electronics.  But in a world where most of us fall into this category when it comes to buying items such as plasma tvs, I am exceptionally thorough both in researching specs, the products themselves and where to buy them.  First, I laid out fairly straightforward criteria:

1. Screen size
2. Technonology
3. Relevant specs
4. Aesthetics
5. Price
6. Where to purchase

Screen Size - This is obviously critical as it will determine a major portion of your viewing experience.  It will also raise or lower the price dramatically, probably close to doubling every time you move up a screen-size increment.  Viewing is a personal choice.  The only objective criteria are the size of the room in which you plan to install the plasma and how much personal viewing pleasure you can afford.  Generally, if I am sitting more than 5' from the screen I want 42" or larger.  Smaller than this and you probably don't need a plasma.  Use the computer screen (hopefully a flat screen LCD) on which you are reading this guide as a gauge.  If it is a typical 17-19" flat screen, ask yourself from how far away do you still enjoy watching moving images on it?  Once you are at close distances and/or opt to buy a smaller screen it is infinitely more economical to buy an LCD screen.  Lest I leave you with the impression that there is little difference between say 42" and 50" (by far the most popular screen-sizes purchased in the plasma marketplace), the difference is huge.  Pictures on the higher end 50" screens are magnificent with lusher color, sharper picture and a true movie theater feel.

Technology - In brief, there are 3 available technologies in the flat screen universe:  Plasma, LCD and DLP.  For sticklers, I am omitting flat screens on antiquated CRT technology such as Sony WEGA.  Plasma is the subject of this Guide and for my money is the lushest, warmest and most true-to-life picture of them all, particularly in larger screen sizes.  Both DLP (Texas Instruments million-mirrors technology) and LCD (your digital flat screen computer screen) provide brilliant picture at cheaper price.  Not as warmly colorful as plasma, but certainly leagues ahead of standard CRT (Cathode Ray Tube) TVs.  For smaller screens, less than 32", LCD may well be the way to go.  The picture is sharp, if a bit harshly light, and the prices at this level are far superior to plasma.  My personal experience with LCDs is with Samsung and I strongly recommend their 23" and 26" HDTV models.  I have next to no experience with DLP although I believe the technology has made serious gains on Plasma and that, particularly at over-sized models, 60" and above, DLP may well be ready to upstage Plasma for those of us who would rather spend $3,000-4,000 than $8,000-12,000 or more.

Relevant Specs - Sifting through the gobbledy gook of pixels, mghz, etc. all came down to picture quality, a built-in tuner, built-in speakers (and where they are located), some audio-visual inputs and PIP. 

• Picture - If you're going for the money of a 50", buy 1366x768 (1024x768 for a 42").  Watch out for 1020x1020 which is really a widescreen, commercial display.  Always look for the higher "native resolution" when it comes to picture quality. 
• Tuner - If the set does not have a built-in tuner like your normal TV, you will need a separate cable box or digital box to receive and play channels.  Since most people have a cable box or DVR, this is usually not a problem but if for some reason you intend to bypass the box and save the $5/month (or $9 for a digital box) and plug the screen directly to your cable outlet, you will need the built-in tuner to change stations. 
• Speakers - Many of the larger sets have speakers only as an option.  If the set is to be hooked to a stereo surround system or just through a local stereo receiver, you don't need the speakers and can often get a cleaner look to go with your purer sound.  But if you have any intention or possibility of using the set clean, with it's own tuner and soundsystem, best to err on the side of caution and get the built-in speakers.  You can pay extra where speakers are optional, but this will add 100's to the price. 
• Inputs - All of these sets come with the basic audio-visual to hook the set up to your cable box, stereo and audio-visual components.  In today's world you want to make sure and have at least 1 HDMI input/output to enable you  to access true HDTV.  In additional to a digital cable box you need this wiring to receive the 720/1080 digital signal.
• PIP - Silly thing.  After narrowing my personal search down to 2- 50" plasmas and going back and forth between them for months, I realized that one of the sets did not have PIP ("Picture-In-Picture").  My advice:  If you share the set at all, particularly with a spouse or partner, get the PIP.

Aesthetics - All normal retail sets of which I am aware come in either black or silver casing.  For me, the silver casing is more "tinny" and machine-looking.  This is particularly true with attached side-speakers which make it look like an overly-large computer screen or digital sign.  This has no bearing on quality!  We are just talking looks.  The black screens are glossy, hot looking things that make any room look that much classier.  Although just my perception (although many others have related this phenomena as well), I also think the black frames create the illusion of a larger, deeper TV space.  The picture seems so much brighter, so much bigger and so much "deeper".  Speakers underneath rather than on the sides are also for me.  There have been some funky, multi-layered constructs of TV-to-speakers, but the subtlety of undermounted speakers is for me.

Price - I lump price and brand together because, once you set your price, you will find yourself in what I view as 3 set categories:  Low, Medium and High End.

• Low sets are all the manufacturers you never heard of (see Chinese or Korean companies I have never heard of) or, if you did, you never heard of them in the context of plasma tvs (Kodak).  Using 50" sets as an example, these are the sets that start to break the $2,000 and below barrier.  Don't be fooled by specs in common with better tvs.  These are not the same, the pictures are grainy, wavy, flitting things and the colors are those seen watching a moving object through colored industrial block glass.
• Medium are where most of us fall.  We are prepared to spend $2,500-4,000 for a fix of the plasma world, but balk at crossing that line and certainly don't want to find ourselves in the $5,000+ universe.  Since Sony doesn't make them and Samsung is really a euphemism for "we're better at LCDs", I think we are down to Panasonic, Pioneer and Phillips.  My experience tells me that Panasonic is by far the most popular in the 42"/50" marketplace.  I bought a Pioneer (see Aesthetics above).
• High this is where your stereo guy steers you.  Mine wanted to sell me a Marantz for $6,000 or a Fujitsu at $5,500.  Of course, the Marantz comes without speakers or a tuner requiring extensive wiring, audio-visual equipment and a Universal remote that can control my heat, a/c, alarm system and, even baby-sit my kids.  I smelled $10-12,000 easy.  I am not doubting the superior quality of this product.  I get what my stereo guy means by the "wavy" picture on lesser sets.  But, c'mon, who of US really notices or cares?  The waviness he is talking about comes in two forms.  One is due to the inability of lesser sets to fully upload the digital signal.  This can be a major problem with Low End sets, but is pretty minor in the Medium class.  For the record, both the Pansonic and Pioneer are outstanding.  The other form is the tendency of these sets to spread out movement.  When someone or something moves it is as if lesser images of their movement follow them.  Kind of like the path of a baseball in Super Slo-Mo.  Again, while technically accurate, this is minor for most of us.  Yes, it could theoretically be frustrating when watching a fast-paced sporting event.  Again, this is a function of price.  For my money, this has been almost unoticeable.

Where -

• Big Box stores are good for seeing the sets in person.  Best Buy (this name must be an oxymoron) and Circuit City were always the most expensive.  They may match another legitimate price, but all this means is that if I am ignorant or lazy, they will happily gouge me.  PC Richard was the best and negotiated even without a better price on the table.  They are just burdened, as are all non-web retailers, with tax and delivery.  The best price I got at PC Richard on the 50" Samsung, Phillips, Panasonic and Pioneer were still more than reputable on-line retailers and compounded by tax and delivery charges.  DO NOT judge the picture by what you see in these stores.  These are solid, digital feeds with unnaturally clear pictures.  I doubt they will give you  a straight cable feed.  In most cases you are probably watching a DVD movie anyway.
• Warehouse stores such as Sam's Club, Costco and Super Walmarts can be great, but you are severely limited in choices and on-site help.  The universe of available plasma tvs is too great to be limited to a couple of Asian-manufacturers, last year's Panasonic model and only a handful in each screen size category.
• The Web leaving aside internet scams this is seriously the way to go.  I used the Plasma TV Buying Guide website to read up on the technologies.  I used DTV City's website to do side by side comparisons as well as familiarizing myself with most sets.  But I bought on Amazon.  Why?  Because they have almost everything.  If you buy a product sold/shipped by Amazon there is no tax and no shipping.  The set I bought retailed for $3,999.99.  The best Big Box price was $2,799.99.  With tax and delivery this ballooned back up to $3,100.00.  By contrast, at $2,499.99 on Amazon, I was blessed with no tax or delivery!  How cool is that?!

I reiterate that I boast no particular expertise in electronics.  The above represents my personal experience and research.  It was well worth it.  I think I did a great job and ended up with a tremendous set with which me and my family are very, very happy.

Please tell me if this was helpful in some small way to your search by responding positively below.....