Eject CD/DVD:
Hold down mouse button
Power on
Keep holding the mouse button
Choose boot up drive:
Power on
Press and hold Option
Recovery mode:
Power on
Press and hold Command + R
Boot into safe mode:
Power on
Immediately after hearing startup tone, press and hold shift key
Release the shift key when you see the gray Apple logo and progress line
Reset the SMC:
Press and hold Shift+Control+Option+Power simultaneously
Hold down for 5 seconds
Release all keys simultaneously
PRAM Reset:
Reboot Mac and as soon as hear boot chime, press and hold the Splat (Command)+Option+P+R keys simultaneously
When you hear the chime again, let go and let Mac boot up
Run diagnostics:
Power on
Immediately press and hold D key
Target mode:
Hold T
Hold T
