2 minor problems - expose hot keys and how to reboot

Hi,
Expose Hot Keys - the ones that work by default did not seem to work... instead, one of the keys modifies the screeen brightness... I was able to change the Hot Keys to other ones via the system settings - and that works fine... just wondering why the originally programmed ones do not seem to work...

After loading a lot of new software, I wanted to reboot single user mode and run fsck to check the file system integrity... Need to hold down the "command s" keys to do this... What is the command key? Also, when do you start holding down the key sequence? or do you just hit it once during the reboot and the system will see it... wasn't able to do it but wasn't sure if I was holding the command key (was using the Apple Key as the command key)...

thanks for assistance!,
SouthSide

the command key is the apple key..your right...holdin down that and s i think should work..continue to hold it down during the start up when you see the grey screen and it should boot up for yah