My favorite example is this: Lets say you want to learn about a new Javascript library. 1. Spend a little bit of time reading about it, so you know about 20%

My favorite example is this: Lets say you want to learn about a new Javascript library. 1. Spend a little bit of time reading about it, so you know about 20% of what you need to know, then convince a group to let you give a talk about using it. 2. Realize, "Oh crap, I know virtually nothing about this, I need to use it for something!" Build something with it and take notes as you go. 3. Your notes can be easily morphed into a presentation, which you give to the group on the assigned date. The deadline forces you to take action, and the doing before the teaching makes you learn a lot of the material before doing the teaching, and then preparing for the final "teaching" part cements the final bits of knowledge you might have missed. If you can't find a group to do a presentation, start a local one! Its really easy with the free tools available online now.