For a true vert ollie, you keep your front foot above the front trucks. In a regular ollie, you want your front foot a little back, so that you can slide it up the board, right? Well, in a vert ollie, you won't be sliding that foot. Just keep it above the front trucks.
Ride straight up the ramp with enough speed to clear it. This will usually take some pumping, or dropping in on the other side if you are riding in a half pipe of some kind.
When you are just before the top edge or coping of the ramp, you want to lean back towards your back foot, push down the tail of the board like an ollie and lift the front foot and nose of the board up off the ramp. The motion is very similar to an ollie, but without sliding your front foot, and with leaning back. Make sure you do lean back - if you don't, you can fly up and over the ramp (if you are trying to do this, to pop up and out of a ramp, that's how you do it!).
When you come back down you'll be riding fakie. Bend your knees, control your board, and make sure you keep your weight on the front foot (the foot that used to be the back foot, but is now the front because you are riding fakie). Slap that foot down when you come back down to the ramp and ride back down the ramp fakie.
This will take a lot of practice, but eventually you'll be comfortable and confident!
