I have my first year students keep a 'vocabulary notebook' where they write any new words that they learn or ones they don't know that they want to find out about. I have found this to be a very effective strategy in my own language learning, but like any practice, you need to make the effort, and make it work for you.
I was grading them for completion today and came across this gem:
Migraine (n.): an extremely severe paroxysmal headache
I would bet my salary that the only word he understood in that definition was 'an'