LG has been around for a while, making lots of electronics. I know them more from cellphones than anything. The best piece of advice I can give regarding electronics, is stick to buying from a company that does it's main business in that market. i.e., I'd buy a Dell laptop, but not a Dell TV.
Use the internet to find reviews from customers. I've seen some TV's at a great price and thought about buying them, until I saw user reviews. Amazon, Newegg, buy.com, circuitcity.com and cnet are all great sites. Search those sites for the model numbers you are interested in to see if users have any reviews. Newegg is my fave resource.
And of course, the best advice I can give you is to always trust your own opinion. If you are down to two that have similar features and reviews, go with the one you think has a better picture. I'm not a fan of plasmas myself, they seem dull. I'm still in the rear projection HD fanclub since you still need to take up space anyways for the receivers, dvd players etc.