Taking pictures of your computer screen is pretty simple on most operating systems these days. Usually, there's a handy shortcut key.
In Windows, that's typically the "Print Screen" button. On a Mac, it's Command+Shift+3.
You can also tweak the Mac screenshot defaults by getting your geek on — launching the Terminal screen and typing in some old-school command-line codes. To change where the screenshot is saved (default sends it to your desktop), you can type:
defaults write com.apple.screencapture location **folder path**
You find the folder path by right-clicking it and selecting "Get Info". It will look something like Users/seamus/Documents/screenshots. Don't include the stars.
To change what kind of file is saved (the default is a PNG) type:
defaults write com.apple.screencapture type jpg
Or you can swap the JPG for BMP, GIF, PDF or TIFF.
Log out of your computer and log back in for the changes to take effect.
Even if you only do it so you can say you've changed some settings via the command line, it could be a tweak worth doing.