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.
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.