Each skateboard wheel is mounted on its axle via two bearings. With few exceptions, the bearings are the industrial standard "608" size, with a bore of 8 mm (or 10mm depending on the axle), an outer diameter of 22 mm, and a width of 7 mm. These are usually made of steel, though silicon nitride, a high-tech ceramic, is sometimes used. Many skateboard bearings are graded according to the ABEC scale. The scale starts with ABEC1 as the lowest, followed by 3, 5, 7, and 9. It is a common misconception that the higher ABECs are better for skateboarding, as the ABEC rating only measures tolerances, which do not necessarily apply to skateboards. Bearing performance is determined by how well maintained the bearings are. Maintenance on bearings includes periodically cleaning and lubricating them . Bearings that are kept unmaintained have their performance greatly lowered and will soon need to be replaced. Bearing cleaning kits are commonly available on the market. The ABEC rating does not determine the speed or durability of a skateboard bearing. In particular, the ABEC rating says nothing about how well a bearing handles axial (side-to-side) loads, which are severe in most skateboard applications. Many companies do not show the ABEC rating, such as Bones Bearings, which makes bearings specifically for skateboarding, often marketed as "Skate Rated". Each bearing usually contains 7 steel or ceramic bearing balls, although other configurations are used as well.
Pop the board in the air – The reason you jump up into the air in the first place is because you’re slamming the back end into the ground (don’t worry, your board is made to take the abuse). It’s the same motion you would do if you were standing near the board and wanted to pop the board up into your hands, except this time, you’re standing on top of it. As soon as you feel the board pop into the ground, kick your front foot up into the air at the same time. The timing on this is important: kick too early and you won’t go anywhere, kick too late and your board will fly out from underneath you.
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.