1. Stay away from the no-name brands. Stick to Samsung, Sony, LG (and MAAAAAAAAAAYBE Visio). Choosing between these brands, though, is like choosing between Chevy or Ford, Coke or Pepsi: no real difference, just individual bias.
2. Bigger is definitely better. It makes HD/4K much more noticeable compared to non-HD/4K, and it's obviously easier to see more things happening on the screen. It also allows you to sit farther back from the screen and have a more open living room/TV viewing room/etc.
3. If you have a choice, get one with 4K capability, because that's going to be the standard soon and you're not going to want to get a new one right after getting a new one.
4. Get a TV with the deepest possible shades of black, because the contrast between black and colors is one of the most important parts of TV picture quality.
5. Get the TV calibrated. It's not useless or a scam, it actually does make a difference. A calibrated crappy TV can look better than an uncalibrated good TV, so keep that in mind.
6. Most TVs now are fairly light-weight when compared to TVs of the past, so they can all be simply set on a table rather than mounted on a wall. Keep in mind, though, that all flat TVs can be knocked over MUCH more easily than old tubes. If you have small children or wandering cats/dogs/iguanas/whatever, always be wary of unsecured TVs on tables or consoles.
7. I'm not a personal fan of the curved screens (personal bias again), but I've heard good things about them. I'd suggest you go to Best Buy or wherever and just give them an eye test, see if you like them better than flat or vice versa.