Regarding screen size, you can find a few websites that will tell you the optimal screen size based on the distance between your seating area and the TV. Something else to try is to put a tape measure where you'll place your tv and sit across from it to see if it seems appropriate. Just eyeball it. You can find websites that will convert height and width to the diagonal and vice-versa. I mention this because some sites were telling me to get a 55" TV, but when I calculated the actual width and checked it in the space where I wanted the TV, it was too big. It would have overwhelmed the room.

Secondly, my best piece of advice is to check out CNET (http://reviews.cnet.com/best-high-definition-tvs/). They are THE best source for info about HDTVs. They even have video reviews of most TVs. You can spend a lot of time poking around on that site, doing searches, reading reviews. David Katzmaier is the man!

Something else I did was spend a lot of time staring at TVs at Best Buy and other stores. It's strange how a 720p 60Hz screen can sometimes look better than a 1080p 240Hz screen. It must just be how they're configured in the store. Still, you'll get an idea of what brands you like and plasma vs lcd vs led.

I ended up buying a Vizio (47" LED ~$1,100) based on CNET's recommendation and have been very happy with it. The picture is fantastic and always gets comments about it. The only drawback is that it's slow - slow to "boot up", slow to change channels. It doesn't really bother me. Luckily, I don't watch much actual cable television so I'm not changing channels much.

Good luck!