READ MORE TECHNICAL BOOKS
I started reading a very good book. I should read a lot more... but my couch is so comfortable, I fall asleep right away, every time I lie down on it. Maybe I should spend a whole day or a day and a half a week just reading technical literature. Most of the time I make the mistake of reading only when I have a problem in the design process.
This is actually not a good idea. You can't prevent all mistakes and/or misjudgments and reading too much and thinking too much can distract you from creative "doing" and trying out, but even after 2 years I'm still a noob and have to accumulate more knowledge.
What I still want to read is "Building Blocks on Tabletop Game Design" by Geoffrey Engelstein and Isaac Shalev and "Players making decisions" by Zack Hiwiller. I've already read a lot of Jesse Schell's "The Art of Game Design", but I think I should start over and underline everything relevant with a pen.
"Relevant" is always a double-edged sword, though.
"Relevant" changes every day in game design and the human being has a selective brain.