Keeping all the above in mind, do the following:
1. Go to your nearest Comet.
2. Find the size you like, then look at the
quality of the picture - clarity, crispness of colour, motion blur (poor quality LCD panels suffer particularly badly from this), and brightness. Also check out the viewing angle - I.E. how far to the side of the screen can you clearly see the image?
3. Specification - yes, it will be HD ready, they all are these days. I would recommend making sure it can handle at least 1080i, again, anything 42" up should do. 1080p is a bonus, but not an essential.
4. Take a note of the model number.
5. Come home, compare online using sites such as Kelkoo and PriceRunner. It's also worth looking at Comet online - they often do the same TV you've just seen in-store for cheaper through their website - you can even reserve online at the web price and pick up from the store. Most useful way of saving money!
6. Plug in, start watching.
7. Grab beer/wine/soft drink.
8. Enjoy!

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EDIT: I can't stress this enough - ignore the brand name. I have a 37" Goodmans LCD, it beat the rest of them in that size class hands down. I personally would shy away from Sony or LG (i have a 42" LG LCD in work, it's not too pleasant). If you are a brand name person, Panasonic Plasma (their LCD's are so-so), Samsung Plasma & LCD, and Philips Plasma & LCD. If you watch a lot of cartoons or animated films (ice age etc), my personal recommendation would be an LCD - plasma doesn't have quite the same depth of colour as the LCDs.