I have put a few guys through IEC. Crazy that some of them will do three years and then drop it, and never get a license. Stick it out.
I have only known one that dropped it because he went ahead and got his license.
Learn how electricity works (IEC will help with this). I know journeyman that are clueless and could get themselves killed.
When someone shows you something, look it up and learn why.

Looking ahead...
When it comes time for the journeyman test, take it as soon as you can. You need to live the test. What I mean is every hour in the truck on the road (if not driving), sitting at home on days off, break time, etc, study. And study as if you were trying for 100%. I have heard too many guys say, "I only need a 70 percent" and they get a 60. When I did my journeyman test, I could have easily passed the masters test, I just had to wait four years (now only two years) to do that.

skinnerback nailed it, memorize everything. When I was studying I had 100 index cards that I did everyday with NEC tables, sections, chapters, definitions, etc. I would go through them, then flip them over and do them again. Take bunches of practice test. Do not just blow through them on guesses, sit and take it as if it were the real thing, look up the answers.