Large power is created at the point of action by applying small power to the point of effort. Application of this concept to skateboarding makes the back wheels the fulcrum, the tail the point of effort, and the nose the point of action. Applying power to the tail causes the nose to shoot upwards. When the front foot of the skater levels the nose at a point roughly horizontal to the ground in anticipation of the tail, soon to be leveled likewise by the skater’s back foot, the process smoothly done creates the illusion of the skateboard ‘sticking’ to the feet.
To get higher ollies, I would suggesting resting your back foot on the very end of the tail and the front foot in the middle of the deck to allow for more slide. Popping as hard as you can and catching your board in the groove of the nose with you ankle practically resting in the groove will level the board out in the air. after this initial movement slide you feet back to the bolts on the tail and nose to ensure a clean landing.