

Open System Preferences ( Apple > System Preferences).To add a hint to your Mac user password follow these steps: The previous suggestion will work only if you can log in to your Mac computer, but what happens if you forgot your Mac password? Or if you have lost admin password for the Mac OS X? If that’s the case, but you have set up a hint, you can request the password hint and see if you can remember your password, this might do the trick and you will not need to reset it. How to Create a Hint for Your Mac Password

This will ensure that if you forget your username, at least you will have a list of usernames to remind you which one might be yours.
