This is less of a hint than a suggestion for a bookmark in your favorite web browser. Apple has a page listing dozens of standard keyboard shortcuts you can use at start-up, with the Finder, and with many applications. If you're a keyboard person, rather than a mouse person, you may find some shortcuts here that you didn't know. At a minimum, it's worth bookmarking this page to have a list of keys to press at startup, if you need to change boot disks, boot in Safe mode or boot from an optical disc (if your Mac still supports that).