Well, one of the funnest aspects of skating, is developing control, form, and style. After you've been skating a while you'll start to notice some people have a little tweak in their ollie. Tweaking is where you kind of dip the board down stylishly at an angle. Imagine this slant mark is the board >>> / Maybe not that vertical, but that is the direction of a nice tweak.
Hopefully, you naturally developed a tweak in your ollie, but if not, make sure you can ollie high with control and a strong grip on the board.
You want to have your front foot with your toes at the heel edge, 45 degree angle, almost like you're attempting a heelflip. Pop your ollie like normal, but now, as you're dragging, take extra pressure off your back foot, and try to slide your front foot onto it's side and forward, do not flick out, just slide your front foot straight up. The first few times, nothing might happen, or you might just launch the board into a crowd of hot chicks you were trying to impress, but don't give up.
Keep practicing until it get's comfortable, and try different footings if mine doesn't work for you. After you're decent at tweaking a little on regular flatround, try taking it to a ledge, or over something. Air time off a ledge or gap gives you extra time and opportunity for a nice tweak. Practicing ollying over stuff will help you get your ollie high enough for more effictient tweaks.
If at first you don't succeed, try, try, try, sit down and drink a soda, try, try, and come back on the boards and ask a intelligible member for some more help. But always keep trying, and don't get too frustrated.
My friend tweaking every last bit of an ollie out.