The dominant foot should be the lead foot on a snowboard. If it isn't most likely the rider is riding and steering from the back of board which while it can be effective, isn't efficient.
Your dominant foot is the foot that you most feel comfortable balancing on.
That is not always the case. Many old schoolers ride with a dominate rear foot, and make more back foot turns. Surfing can be more rear foot dominated too.
I personally am goofy, and my front foot is dominate. I skateboard and surf goofy, so that helps. I find my style is both rear foot in the deep pow, and pretty much neutral in all other conditions. With some of the new dual rocker and tapered shapes ( Never Summer Summit), I feel REALLY comfortable riding basically centered in the deep pow. It is truly revolutionary.
The whole sliding on the wood floor trick works for many. More athletic dudes can go both ways, and they should go with what feels more comfortable when skating to the lift, or if they ride a true twin etc....
pray for snow.