Keyboard Shortcuts
When I was first starting to learn how to code, I thought that I should dedicate all of my time to learning how to construct efficient methods, mastering syntax, and figuring out how to domain model. I powered through a ton of labs trying to make tests pass without spending time thinking about my workflow outside of solving problems.
Big mistake. Once you're a programmer in the real world, becoming more efficient as maneuvering around a computer is essential because it'll help you write code way faster, which increases your productivity and ultimately your impact. I never thought I'd say that. To me, it was always one of those things that productivity gurus overemphasize, but I suppose they are right in the end.
Enter shortcutfoo.com. For $8 a month, it'll change your life. I've been practicing my keyboard shortcuts every few days, and I've become a lot better at writing code faster. More specifically, I've been doing the Dojos for Sublime, Github, Gmail, and the command line, but I'm hoping to pick up vim soon so I can spend all my time in the matrix.
At the very least, learning keyboard shortcuts will make you seem like you know what you're doing, so if you have time, try it out. Your fellow programmers will respect you more for it.