To open bootup menu at start up: hold volume up and press power button to start mobile device.
To take a screen shot: hold down volume down, and hold power button for 1 second (doesn't work for 4.0.3 on Nexus S).
Multitasking:
To open multi-tasking list: hold home button for 1 second
To kill a task: bring up multi-task list and swipe item you want to kill.
