The most common shape in skateboarding is called a popsicle shape. It has a curved tail and nose and features concave, which gives the board it’s shape. New skateboarders looking to learn how to carve, push, ollie, kickflip, and grind boxes, ledges, and rails should start with a popsicle shape. If you’re interested in knowing, we explain selecting a board by width, riding style, and board shape in the skateboard decks section of the buyer’s guide.
So the proper foot placement for the ollie is with the ball of your back foot horizontal on the tail of your skateboard. And your front foot centered on your board right behind the front trucks. You may find that moving your feet around in different positions are more comfortable. This is fine, everybody can learn how to skateboard their own way.
A rushed take-off might be the problem here. Steps 2-4 of this trick tip could help you out. In order to make your feet “stick” to the board, you have to do the movement fluidly. But don’t stress yourself out! You should rather start with some preliminary exercises until you feel safe while ollieing. It is also important to pull your foot up to your board’s nose in a straight manner to prevent it from spinning.
When I was about 10, I broke my first skateboard by riding it into a ditch. A decade later, in college, I broke another skateboard within an hour of owning it (surely a record) in a short-lived attempt at doing an ollie. (Surprisingly, the store accepted a return on that board even though it was in two pieces.) Then I was gifted a really nice, high-quality skateboard. The first thing I did with it was ride it down a big hill, a valiant but ill-fated adventure which ended with me jumping off the skateboard, rolling down the grass, and arriving scraped up, deflated, and rather disoriented near the entrance to my college cafeteria. (In my defense, the wheels and ball-bearings on that skateboard had been pre-lubricated to minimize friction, and why would anyone do that, that's just crazy.)
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.