Norman Ramsey made some great points about how tips could be improved. My problem with tips of the day (and I'm speaking as someone who's implemented them in my own apps) is that they are not timely and a bit too intrusive. The typical tip of the day comes up when you start the program, and requires a button click to make it go away. When I actually see a useful tip, my train of thought is usually "I'll have to remember that when I do option ". Of course, it's forgotten by the time I get around to using . And clicking OK during program startup gets old fast, I'll usually disable the tips after the first dozen or so.
My suggestion would be to go the next step and make the tip of the day much more context sensitive. For example, if the program detects that the user is constantly going to Edit | Copy and then Edit | Paste, a good tip would be "Not for nothing, but CTRL+C followed by CTRL+V accomplishes the same thing" and tell them right when they are clicking away at the menu like a lost monkey, not during program startup. Oh, and don't interrupt their work by forcing them to click OK.
What I just suggested - is that what that damn paperclip dude used to do?