After you’ve properly applied a burst of force to the tail, the top-side of your front foot’s toe should start dragging up your board almost automatically. Eventually, the higher you are able to bring your front foot during lift will determine the apex of your ollie, so work gradually towards lifting your front foot as high as your body allows. Skateboarders who record the highest ollies usually (somehow manage to!) bring their feet higher than their hips!
You can learn to ollie while standing stationary, or while your skateboard is rolling. Ollying while standing still works the same way as while rolling, but I think rolling ollies are easier than stationary ollies. If you would like to learn to ollie with your skateboard stationary, you can place your skateboard on some carpet or grass to keep it from rolling. If you prefer to learn to ollie while your skateboard is rolling, don’t go very fast at the start. Whichever way you learn to ollie, once you feel comfortable you should try to ollie the other way as well.
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.
The skater can gain greater clearance from the ground by jumping higher, popping faster, sliding the front foot farther forwards (starting the jump with the front foot farther back), and pulling the legs higher into the chest to raise the feet higher. Skaters attempting record-setting ollies even contort the legs so that board and feet are not directly below them, allowing the board to rise at or just below the level of the pelvis.
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.