keyboard shortcut More at @ - http://support.apple.com/kb/HT1343
To use a keyboard shortcut, or key combination, you press a modifier key with a character key. For example, pressing the Command key (the key that has a symbol) and the "c" key at the same time copies whatever is currently selected (text, graphics, and so forth) into the Clipboard. This is also known as the Command-C key combination (or keyboard shortcut).
A modifier key is a part of many key combinations. A modifier key alters the way other keystrokes or mouse/trackpad clicks are interpreted by OS X. Modifier keys include: Command, Shift, Option, Control, Caps Lock, and the Fn key. If your keyboard has an Fn key, you may need to use it in some of the key combinations listed below. For example, if the keyboard shortcut is Control-F2, press Fn-Control-F2.
Here are the modifier key symbols you may see in OS X menus:
(Command key) - On some Apple keyboards, this key also has an Apple () logo (Control key) (Option key) - "Alt" may also appear on this key (Shift key) (Caps Lock) - Toggles Caps Lock on or off Fn (Function key)
Press the key or key combination until the expected function occurs/appears (for example, hold Option during startup until Startup Manager appears, or Shift until "Safe Boot" appears). Tip: If a startup function doesn't work and you use a third-party keyboard, try again with an Apple keyboard.
Key or key combination What it does
Option Display all bootable volumes (Startup Manager) Shift Perform a Safe Boot (start up in Safe Mode) Left Shift Prevent automatic login C Start from bootable media (DVD, CD, USB thumb drive, and so forth) T Start in FireWire target disk mode N Start from NetBoot server X Force Mac OS X startup (if non-Mac OS X startup volumes are present) D Use Apple Hardware Test Command-R Use Recovery (OS X Lion or later) Command-V Start in Verbose Mode Command-S Start in Single User Mode Command-Option-P-R Reset NVRAM / parameter RAM Hold down the Media Eject (⏏) key or F12 key, or mouse or trackpad button Eject removable discs
Startup key combinations for Intel-based Macs
You can use the following startup key combinations with Intel-based Macs.
Press C during startup Start up from a bootable CD, DVD, or USB thumb drive (such as OS X install media). Press D during startup Start up in Apple Hardware Test (AHT). Press Option-Command-P-R until you hear startup sound a second time. Reset NVRAM Press Option during startup Start up in Startup Manager, where you can select an OS X volume to start from. Note: Press N to make the the first bootable Network volume appear as well. Press Eject, F12, or hold the mouse or trackpad button Ejects any removable media, such as an optical disc. Press N during startup Attempt to start up from a compatible network server (NetBoot). Press T during startup Start up in Target Disk Mode. Press Shift during startup Start up in Safe Boot mode and temporarily disable login items. Press Command-V during startup Start up in Verbose mode. Press Command-S during startup Start up in Single-User mode. Press Option-N during startup Start from a NetBoot server using the default boot image. Press Command-R during startup