Traditionally a
vert skateboarding trick, though it has
weasled its way into
street nowadays. Its a relatively simple trick, especcialy in street.
There's no special stance for this trick. I'll start with the street version: Pick out a low object (like a low bench) to start with, but not so low you don't need to ollie to get up onto it. Approach the object head on at a medium speed, so as to not slide. Once you are close to the object ollie and slide your front foot right up to the nose. Careful not to do this too quickly, because if you do you will just bring the board back down to the ground before even getting higher than the object - so only reach the nose once you are over the object. Your nose should hit the object and you should stall there (note: this can be bone jarring and unbalancing). Once there keep your weight on your front foot until you want to stop stalling. To do so, simply put wait on your back foot as if you were dropping in on a ramp. You are now riding off switch.
Now the vert version: As you are rolling up the transition start putting your weight on your front foot. Once you reach the coping you should begin to tip forward. Slide your front foot up to your nose and as you continue to tip forward you should now have your nose firmly stalled on the coping. Drop in and ride away (note: you are dropping in switch this time).