I'm just going to back up what other people said, and add some other stuff.
First, make a list of sets within your budget and some general criteria (size range, make etc).
Yeah, plan for the future. Think about stuff that you may buy in the next 2 years or so. Chose an input method for these and and all the stuff you have at the moment. Write these down, and adjust the list to get a new list of sets with this set of inputs or better. Never compromise on inputs.
Then narrow the list down by looking at LOADS of reviews. Try out as many as possible too. Especialy if you can do so with the equiptment you use (xbox 360 mainly) and without someone breathing down your neck.
Basicaly, keep narrowing down your list to one set, and you will be sure that it is the right one. Then check to see if there's a new model just around the corner, and if not, you're all set.
Anyway, i always follow this advice for anything i buy, and am rarely disapointed. I use a Samsung 26" HDTV and i love it. And even better, i bought it from costco, so i can return it for a full refund, no reciept needed, no questions asked. I've had to replace it once before, and they didn't even look at it. Costco rules.