Undoubtedly, everyone’s closed a file that hadn’t yet been saved, and gotten the dialog box asking if you’d like to save the file before closing and losing its contents. In most cases this is probably a nice reminder, but there are enough occasions where I was using a text file or an image file temporarily and had no desire to preserve it any further.
I’m definitely more a keyboard-jockey than a mouse user – I just feel more efficient with my hands on the keys is all. So it can be annoying when I have to move my hand to the mouse and click the “Don’t Save” button in those warning dialog boxes. True enough, that hitting the ‘Tab’ key cycles through those button options, but in my experience, hitting ‘Enter’ when over the button you desire is flaky at best.
So in the event you want to choose the ‘Don’t Save’ button (from your keyboard), hit CMD-D (assuming the ‘D’ stands for ‘Don’t'). You should actually be able to use this tip for most warning dialogs, swapping out the ‘D’ for the first letter of whatever button you want to choose. It’s worth mentioning too, that hitting CMD-D executes that selection immediately, not requiring an extra keystroke to hit ‘Enter’.