When learning it, you will, slip and fall. Feel like an idiot doing something over and over again and not getting it, feel fear bcos you don’t know what's going to happen to you once you pop the tail, jump and slide your foot and then you land. Will you land on your board, will you be on the pavement? Will you slip out, will u kick the board away, will you land primo? No one knows but you gotta try it out and find it out yourself. Whatever it is, don't give up cos it's the strength to persevere, be crazy persistent to achieve and most of all being patient in learning and progressing that let's you earn the skateboarder title for your ownself.
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.