How do you know which ones are good, which ones are not?

Tweet

So, you go out to shop at an electronic store, hypothetically. There is a shell full of television; or plenty choice of digital cameras; or plenty of other electronic devices, how do you know which one is a good choice, and which one is not base on your glances at them; also giving that the stores listing the description of each one of them, like their component parts etc...... How would you pick them? The only way to get a good one just base on the brand name; or you did research on their consumer reviews before you go to the stores. I think our shopping experience with those electronic appliances base on our luck. What is your advice?