Know the overall layout of the NEC - Chapters 1-4 are general, 5-8 are more specific, know the appendix's, and know where definitions are.
Then know where the most common articles are - feeders, branch circuits, grounding, receptacles, where ground fault protection requirements are......
My PE exam had a question about ground fault protection for feeders - I knew there was an article that covered feeders, and that was a good place to look first. A quick scan of 215 and there is the answer word for word.
So in general, you just have to be familiar with the overall layout.
And if you can't find the answer to a couple of questions, don't sweat it. Move on, and then come back to those. They don't expect you to be perfect.