Tell a friend to creep up behind you when you are not expecting it and push you lightly forward. The leg that you first step forward with to stop your fall is the leg that should be front leg on the snowboard.

There are many "gimmicks" out there that sometimes work for some people (and not for others). I'd say the best strategy is to try both methods (it doesnt take that long to take your bindings off and put them back in). If you ride with a duck stance its even easier as you can just try both out comfortably.