Want to learn something well? Then figure out how to teach it. Think you know something? Offer to stand in front of a room of your peers - who can (and will) call you out if you're wrong - and act like an expert. Or write it up and put it on the Internet for folks to pick apart with researched references. Do that enough and you will get pretty good.
I didn't study for the Master exam. I wrote an hour-long class for each topic on it and taught that to my coworkers.
When you learn something for yourself, you tend to learn it from the 'How do I use this to solve my problem in my environment with my constraints'. When you write a paper or presentation, you approach the topic from many points of view - different environments, different scale, different regulations. Thus the phrase "You don't really know something until you can teach it to someone else". Learning a topic from that angle forces you to work with the options and parameters you normally wouldn't in your environment but others would in theirs. Done properly, writing and presenting force you out of your comfort zone, and that's when you start to grow.
I gotta admit, having a stranger come up to you at a conference excitedly telling you what they did with what they learned in your class and how much that improved their life is a really, really, cool thing.