I was a little surprised that I never posted this link, actually...
Hotkeys (or keyboard shortcuts) are one of the best ways to make yourself more efficient in a program. For example, tonight in my CIS 127 course, we were doing hyperlinks in PowerPoint. Part of it entailed creating something, and then putting it on ten slides.
Rather than copy and then move down a slide, right click, and then paste, move down a slide, right click and paste, etc., it can be much quicker to move down a slide and use the hotkey, control+V (hold down control, and hit the V key).
I'd never say it makes sense to memorize every hotkey in the program - that would be silly. Instead, I would say that if there is something you do often, you can make yourself more productive by finding the hotkey for it. If you find yourself clicking around, poke around for a hotkey. It's probably there.