I've been a big fan of taking screenshots for quite some time now. It's a great way to share information with someone or to quickly capture inspiring ideas you find on the web. A few months ago, I found a program called Skitch for Mac. It's an incredibly easy to use App. Simply hit the Screen Snap button at the top and it gives you a few options of what kind of screenshots you want to take. You can do a full screen capture, selection, or just a timed screen snap.
My favorite feature is probably that when you are done screenshotting, you can quickly edit it. For example you can highlight areas, add boxes, arrows, and even pixelate the sensitive information you don't want others seeing. This process would take a LOT longer in another editing program such as Photoshop.
When your're done, just select which format you want to export as then drag and drop. Another cool feature is it automatically syncs with Evernote so your screenshots are always with you.
Check it out on the App store at https://itunes.apple.com/us/app/skitch/id425955336?mt=12