My intention with this is to point out a few things that you can use when deciding what TV you should buy and similar products. I will divide it into steps so its easy to follow:
1. What are you going to use the product for?
For example a TV. Are you going to use it for gaming, watching movies, only watching TV, hook it up to your computer etc. Its important to know what you are gonna use it for so that you can find the best TV possible that does all that you need for the least amount of money.
1b. If your buying for example a TV and a gaming console, make sure the TV is up to what the console requires. For example check the HDMI standard that the console has and the standard that the TV supports. If you are buying a Wii, you don't need to buy a Full HD TV or even an HD TV for that matter due to the face that the Wii only supports up to a resolution of 480p. And HD is 720p and above. (Although the next Wii might be released within 2 years so it might be worth to buy an HD TV anyway for that matter and more and more channels are transmitting in HD so an HD TV is an investment in the future.)
2. How much are you willing to spend on the product in question?
Its very important to be realistic about this. Especially if you use some sort of credit-card to buy the product. GOLDEN RULE: Make sure you make a payment plan that ensures that the product is fully paid when the warranty ends. No one wants to sit there with a credit-card debt and no product.
3. For how long will it fulfill your needs? Do research on upcoming products in the same field. Will it still do in 5 years? Do you really need to buy this or is it the perfect time to upgrade/buy something new?
4.When you find the perfect product, make sure it has the lowest price you can possibly find. Why pay more than you have to? If you don't want to buy it on the internet, check the stores in your area and see if any of them has offers like: "We will match any price if you find any of our goods for a lower price in the area" This is kinda common.
5. If you plan on buying it and pay it off, be sure to check the interest and calculate how much it will cost you. Even if something is cheaper in one store and you want to buy it with a credit card, the cost might be higher in the end then buying it in another store where it costs a little more, but have a much lower interest that makes it cheaper in the end if you need pay it off.
Good luck with your purchase :)