Chocks on..
I do agree with the above said:
Chocks on - Brakes Off
At my last employer we the procedure only to leave the breaks on during very windy conditions (eg +35 kts..), but this is off course a company procedure and might be related to the aircraft type (crj)
now, here in the world of business aviation: NEVER leave the park-brake on, when you leave your aircraft, ´cause it is quite common that your aircraft is moved to a different parking apron after you left...
we even carry our own set of chocks on the plane because you never know where you end up in the end of the day.
my 2 cents
welle