If you're thinking of picking up a new TV, now is a great time. Prices are low, and there are a lot of options. The most popular size is 46-51 inches, and the most popular type is LCD/LED, which gives you a better bang for your buck than Plasma. There are a lot of great TV deals to be found, just keep a few shopping tips in mind before you head to the store.
Stay on budget. Get a general idea of what you're looking for then do a quick online search to see what price those TVs cost. Stick to that budget. When you get to the store a lot of TVs look great, and it's easy to get caught up and overspend.
What features do you want? 3D and WiFi are popular features right now. I like WiFi, not crazy about 3D. I suggest looking for a TV with WiFi built-in, or at least WiFi cable that you can use WiFi with the addition of an adapter. Services like Hulu and Netflix Instant are gaining popularity and you don't really want to watch movies on your laptop, this way you'll be able to easily watch them on your TV.
I'm not a 3D fan, but whether you want 3D or not is up to you, but be warned: Sometimes the 3D glasses can be pricey. If you have to outfit a family of four in 3D glasses that could be a significant amount of additional money you need to spend.
Put it on the wall. If you're going to mount the TV on the wall. Make sure you measure the wall, and bring measurements with you to the store. If you have little kids who climb, I suggest putting it on the wall out of reach. This will cost you anywhere from $200-$500, but in my opinion the peace of mind is worth it.
Are you thinking of getting a new TV, or did you get one recently? What room is it for?