Shop online first. AVSforum is a great place to learn. Once you discover what you want that place also has user threads with settings that seriously improve picture quality.
Smart shoppers look at returns too. My son got a nearly new highest rated TV, Panasonic plasma (TC-PVT25), at a Best Buy Magnolia store for thousands off the list price. The store clerk didn't know how to check for number of hours used and we did.
Absolutely, I use the The Spears & Munsil High Definition Benchmark Blu-ray Edition (got it with my OPPO) and DVE HD Basics. Also have a Spyder3TV colorimeter which I use with HCFR software instead of Datacolor's. Makes a calibrated Vizio look like a uncalibrated 6K Pioneer, almost.