Dead (sub)-pixels how to recognize?

This could be a stpid question, but here it go’s:

I’m gonna buy a new PC with monitor. This monitor is going to be a LCD. We all know that LCD screens can have dead (sub)pixels.

I have no experience with LCD screens and dead (sub)pixels and because of that I don’t know if you can easily see them when the screen is on.

How am I going to recognize a dead (sub)pixel??
Is it immediatly obvious when there’s a dead (sub)pixel (even if it would be in a corner)??

I have to drive a long way, so I don’t want to drive back to the company I’m gonna buy the screen.

Explanation by Vincent Alzieu of Tom’s Hardware page.

Some dead (sub) pixels are not easily recognized.

Each pixel is made up of one red, one green and one blue sub-pixel.

A defect in a sub-pixel is not very visible, and can often only be seen against specific backgrounds.

Adjacent sub-pixel defects appearing close in proximity are more visible than “geographically dispersed” defects.

A full-pixel defect (all three R/G/B sub-pixels always on or always off) is quite visible.