Neat Windows Trick
When somebody's calling me with a computer problem, or they see an error on their screen, they'll usually tell me something generic like "I got this error on my screen." Oh, that's useful. "What was the error?" "Oh, I don't know, it just went bonkers." I go on to tell them I need the exact error message before I can diagnose something, I don't care how cryptic it is. Then they try to read it to me, and something gets lost in translation.
Well apparently you can hit ctrl-c on any Windows dialog box, and have it copy its contents to the clipboard where you can then paste it into Notepad, or whatever. Then they can copy the dialog into notepad, print it, or e-mail it my direction, making it far easier for me to fix something. Thanks to Neil (who has a much better graphical demonstration) for pointing this out.