1. Maximize the window you'd like to capture (maximizing just makes it easier for the person to see the screen that you wish for them to see).
2. To copy/capture the current window, hold down ALT + Print Scrn at the same time. To capture the entire screen, just press Print Scrn.
3. Open a new document in MS Word, MS Photo Editor, or Adobe PhotoShop.
4. Paste the screen shot by holding down CTRL and V at the same time.
5. Print the document when you're finished pasting screen shots. Or, simply email the document to someone that might like to see it.
For the Mac, there is a wonderful tool call Grab! It's an application that is part of the operating system and is very handy for capturing information on your screen.