How to rate a good set of milled grains from bad?

So getting ready to do my first AG batch Saturday, i will be milling in the brew shop. Are there any guides(with pictures/etc) out there that explain what I should be looking for after running through the mill? Some people say Local brew shops sometimes need you to run through the mill twice, but then i read milling too much can cause off flavors...

The grain should be crushed into small bits but the husks should still be mostly intact but split open. You don't want flour and shredded husks. You'll get great efficiency but never get the wort out because you'll have a terrible stuck mash.

However, if you are BIAB then it can be crushed down to near flour since the bag acts as a filter.

Visit braukaiser.com and you'll learn more than you ever thought there was to know about AG brewing. Even if you only understand 10% of it, you'll be much better off. You can look at the pictures he has, but generally you want relatively intact husks while breaking the interior into as many pieces as possible. If you have whole, uncrushed grains, run it again. Brew shops generally mill with a slightly wider gap so that their customers avoid stuck sparges. That they can sell a little extra grain is a welcome side effect. Your recipe is probably written for 70% efficiency, although 60% is probably a more realistic expectation for your first AG brew. I would keep some light DME on hand in case you wildly undershoot.