In order to learn the nollie, you should already be able to do the regular ollie. Both tricks are similar – the only difference is that the movements of a nollie go in the opposite direction because you pop off with the nose instead of with the tail. Performing a nollie might feel a little weird at first, but as you practice it you will get used to the reverse movement.
NOLLIE - STANCE: REGULAR
In order to do a nollie, you should crouch down a little prior to the pop. The placement of the feet is the same as for an ollie, only now it's shifted onto the nose. That means that the front foot is positioned at the very front of the nose and the back foot is positioned right before the bolts of the back truck.
Here's where things become fast again. Out of the crouched stance, you jump up and use the momentum to press down the nose. At the same time, your back foot pulls towards the tail.
If you have executed Step 02 in one fluid, harmonic motion, your board has popped off the ground and is now at the highest point of the trick: it's in the air with both feet above it.
Now comes the easy part. Keep your feet above the deck and your shoulders parallel to it. That way, you can enjoy the last milliseconds of the flight and wait until you stick the landing and finish the trick by rolling away with balance.