Derek Lieu's Keyboard Shortcuts
The easiest way to become a more efficient video editor is to take the time to customize your keyboard shortcuts and then use them. It's simple, but effective and Derek Lieu gives some great suggestions on where to start if you're not already doing this.
While the video below is focused on Premiere Pro CC, his full post gives a breakdown of the same shortcuts in Final Cut Pro 7, FCPX, and Avid Media Composer. It's definitely worth your time, even if you prefer one of those.