The proper technique is ridiculously subtle.
http://support.apple.com/kb/HT1630
That support article is a spiritual ancestor of the Antennagate defense press event.
It's not that subtle. Just don't try to wrap it really tight, which would put a constant strain on the wire where it enters the brick that would last until you completely unwind the cord again.
Frankly, everything in that document just looks like common sense.
