Here is some startup shortcuts which will be helpful for your better experience on Mac and make you learn about tricks on startup of Mac. If you don’t have any Mac device then you can try Mac OS X on any non-brand PC, and this will helpful for your user experience
OS X safe boot- Press and hold SHIFT during startup
Force OS X startup- Press and hold X during startup
Choose startup disk before booting- Press and hold OPTION during starup
Start up from a CD or DVD- Press and hold C during startup
Startup in Firewire Target Disk mode- Press and hold T during startup
Bypass primary startup volume and to choose a different startup volume- Press and hold CMD + OPT + SHIFT + DELETE during startup
Eject CD on boot- Press and hold the mouse button once you push the power button
Startup in single-user mode (command line)- Press and hold CMD + S during startup
Start up in Verbose mode- Press and hold CMD + V during startup
Sleep immediately without confirmation- CMD + OPT + EJECT
Restart immediately without confirmation- CMD + CTRL + EJECT
Shutdown immediately without confirmation- CMD + OPT + CTRL + EJECT
Show dialog with Restart, Sleep and Shutdown options- CTRL + EJECT
Put display to sleep- CTRL + SHIFT + EJECT