Because I always forget:
1) Open a command prompt (Start->Run->cmd.exe)
2) Type “net stop wuauserv” and hit enter.
3) Enjoy no longer getting knocked out of StarCraft 2 while you’re in the middle of your rush.
(Tested in Windows XP, YMMV in other operating systems.)
I prefer
net stop "automatic updates"
Longer, but easier to remember and type.