I am not sure that working at an electronics store makes someone knowledgeable in this area, usually they set the TV to "Dynamic" or "Demo" mode and leave it on display.
A lot of the calibration is going to depend on you. How much light is usually on when you watch TV? What angle do you watch at? etc.
I usually suggest people play with the default colour settings, and see if any of those work for them. If not, you may want to look into something like the
THX Tune Up app. It's free and gives you a quick way to do some basic calibration.