By reading (esp. code), writing code, and reviewing (i.e writing about code). Reading, esp. code (including learning new languages and reading in them), shows

By reading (esp. code), writing code, and reviewing (i.e writing about code). Reading, esp. code (including learning new languages and reading in them), shows me new paradigms, new idioms, new ideas, sometimes parts of new ideas which may click together later. Sometimes the patterns may however be subtle and not easy to notice by pure code reading; in such cases reading free-form prose (blogs/etc.) can help notice them. Also reading code invariably provides examples of bad code, to be remembered as a warning and something to try to avoid. Writing code introduces need for actually choosing some of the learned approaches, excercises the learned theory, ingrains it, shows the shortcomings and costs of particular patterns/approaches, their nuances, where they fit and where they don't, allows to experiment with them. "Exchange with coworkers" is usually also reading in my case, i.e. code reviews. And I just realized that also doing code reviews helps me improve coding in one more way: I sometimes discover stuff when I'm trying to express in words why I find some peer's code jarring, troublesome, or confusing.