Back when I worked exclusively on a Windows machine, I loved using Screenpresso for the ease with which it allowed me to do screenshots and screencasts (if you’re still stuck on Windows, go buy it, it’s worth it).
But now that I’m on a Mac, what to do?
So to start with just press SHIFT–CMD–4 and you can take a screen shot. It’s a native Mac thing.
If you have Dropbox installed go to Preferences | Import and tick the Share screenshots using Dropbox option.
If you want to do screencasts, then fire up QuickTime Player (CMD–SPACE | Quicktime ↩) then press CTRL–CMD–N to start video recording.
That’s how easy it is on a Mac.