Missing brick list

Hi all - I'm just about to break my non-lego cherry and start the King UCS Millenium Falcon & X-Wing.

I hear about issues if missing bricks.

What's the guidance on compiling a brick list? Are they coded?

Also, it would be easier to to stop and request missing brick by missing brick...but that would not only be a bain to all but also the Carbon Footprint Police would be all over me!!

So I assume there is a work round? Proper newb question but thought ask.

Cheers guys