Damn glad I did, 'cause I just had a toilet tank crack and - if I hadn't known this - the whole place would've been flooded.

I also had to do this years ago, at my parent's place, when their washing machine tube cracked (if you have rubber, change 'em over ASAP!).

i had a plumber working on fixing a wall in the bathroom, and an old connection broke, we were both running around trying to figure it out and finally just went out front of my little complex, found a main valve under a heavy cover, and turned off everyone's water till he fixed the connection. That was tense... I was throwing towels down to slow the water from going out of the bathroom.

ufoclub said:

"Tense" is the word! Luckily, I was able to move fast enough to contain it to the bathroom!

Yes - in each room and the main cut off

Yes but I would shut off the gas long before I thought about the water.
And I wouldn't turn off the water until I filled everything that would hold water.

Turning it off you will pressure and in a break it may be awhile before you get service.