Prevent automatic login

When you see the progress indicator (looks like a spinning gear), hold down the left Shift key

Prevent Login Items and Finder windows from opening when logging in

After clicking the Login button at the login screen, hold down the Shift key

Start up from a CD

C

Start up from the default NetBoot disk image

N

Start up in Target Disk Mode

T

Select a startup disk (on some computers)

Option (To open the optical drive when choosing a startup disk, press ⌘-period.)

Start up using Mac OS X rather than Mac OS 9 (if both are on the same volume)

⌘-X

Eject removable discs

Hold down the mouse button

Reset Parameter RAM

⌘-Option-P-R

Show detailed status messages (verbose mode)

⌘-V

Start up in single user mode

⌘-S

Start up in Safe Mode (Only essential Mac OS X items are started. Some features and applications might not work correctly.)

Hold down the Shift key immediately after the startup tone and release when you see the progress indicator (looks like a spinning gear)