In 1978, Alan Gelfand, who was given his nickname "Ollie" by Scott Goodman, learned to perform no-handed aerials in bowls and pools using a gentle raising of the nose and scooping motion to keep the board with the feet. There are numerous references to Alan Gelfand's Ollie with most notably pictures in the 1970s skateboarding magazine "Skateboarder".
Both your height and weight should play an important role when you are choosing a skateboard. You need to find a skateboard, which fits your weight and height. Picking one, which is either too small or too big might only cause you to experience difficulty controlling it, especially if you are still a beginner learning the ins and outs of skateboarding.
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.