In Lesson 23, Ben talks briefly about a nifty tool for grabbing screenshots called Jing. I also use Jing as my go-to screengrab tool on Windows. It also allows you to record up to 5 minutes of screen video, with audio! Great for a free tool.
I just wanted to share for Mac users, I recently was shown that OSX (at least in Yosemite) has a built-in screenshot tool that is super-easy to use: Simply press Shift-Command-4 (the number 4) and your cursor will change into a little crosshairs, you click and drag to create a rectangle and when you let go whatever is in the rectangle will be saved as an image and placed on your desktop.