Plan reviewer is not my primary job, but is one of my responsibilities and I've reviewed a lot of plans over the years. One thing to bear in mind is that you're not the designer, and there are multiple ways of doing things you may not like, or may see a better way, but you can't really reject. Nobody likes being told to do something "just because", and it's good practice to start citing specific code violations when you do reject a drawing, or at the very least, be able to cite specific code violations for things you mark up if they question it. But there are always exceptions; if you're an AHJ, use 90.2(C) where prudent. The codes are all about minimizing risk, and if other factors adequately mitigate risk, some code violations are sometimes acceptable. And don't forget there are other codes besides NEC that must also be followed; you need to be looking out for the electrical impact for the other trades, and will have to get with the civils and MEs to review portions of their prints, too. For a lot of this stuff, if you don't catch it or force them to comply, chances are, nobody will!
In time, you'll gain a working relationship with a lot of the engineers you work with, and a quick phone call can go a long way. And I can garuntee you that you will start to recognize specific engineers/draftsmen from their work, regardless of who actually signed the title block. And you'll know who you really only have to give a quick once-over and who gets the 9th degree.
Don't be afraid to reject drawings for lack of information or to ask for clarification- it's in everyone's interest to catch problems at design time as opposed to inspection, and you can't do that if they've just thrown a few lines on paper.
And lastly, sometimes, the drawings are simply WRONG. And I don't mean poor design, I mean, they're not accurately showing the existing condition and are simply wrong. These can be very difficult to catch but can lead to all sorts of problems down the road; if you suspect an error or see a serious pre-existing problem, bring it up to the engineer. And if practical, go to the site and look first-hand.
