CG Channel has an interview with VFX supervisor Rob Nederhorst (Thor, Captain America, etc) and a preview video of his upcoming Gnomon Master class for compositing anf VFX.
"CGG: So what are those ‘little things’? VFX artists get to see a shot over and over again, but the audience only sees it once. How do you pick out the details that really matter?
RN: This is one of those things that just takes experience to realize. We all want the work to be perfect, but it rarely is. If you don’t notice something in the first two or three plays, in theory it won’t be noticed by an audience. But you never play it two or three times.
The other thing we do is always look at things in the context of the cut. That’s key. Sometimes the individual shots have issues that are just not apparent when viewed in the cut."