How to take a screenshot.

Windows:

To capture the entire screen, press your PrintScreen key on the keyboard. You can then open a Word Document or Microsoft Paint and choose Edit > Paste, or try pressing Control-V

To capture a single window, press Alt-PrintScreen. You can then paste this into Word or Paint also (Outlook works as well if you have it).

To capture a part of the screen in Windows 7, click on the Start Menu, then Programs, then Accessories, then Snipping Tool. If you use this frequently, right click on Snipping Tool and choose Pin to Start Menu. With the snipping tool, click the New button, and then select the area of your screen you would like to capture. You can then save this using the File menu in Snipping Tool.

Macintosh OSX:

The easiest one to remember (since remembering all the different key shortcuts can be a bother, especially if you switch between Mac and Windows frequently), is Command-Shift-4. This will allow you to select an area of the screen, and it will automatically save it to your desktop (typically). You can then do whatever you like with it (upload it to your blog, Facebook, Flickr, Picasa, WordPress or other), or insert it into a document.