The Ollie manual is a good trick to help develop your balance and Ollie control. The idea is to Ollie and land on your back wheels, riding a "wheelie" for a distance before setting the front wheels down. It can be done on the flat ground or over an object, but is most commonly done up onto an element, like a curb or block. It requires a fair sense of balance, and you should be comfortable ollieing. It might be good to get accustomed to manualling on flat ground before ollieing onto something, but a curb is a good element on which to learn the ollie manual. Ride at the curb at a normal Ollie speed - you'll want to go fast enough to get up onto the curb and still have momentum for the manual. Pop into an Ollie and get up over the curb. Instead of leveling the board in the air beneath you, keep your leading foot up and your weight centered over the back wheels. The lower you pop your Ollie, still clearing the element of course, the smoother you will land on your back wheels and the easier it will be to gain balance once on those wheels. Once on them there back wheels, you'll notice your body arched forward over your board as you ride the manual. This is how you keep your weight balanced on the back wheels. It is useful to try and manual a set distance, like to a line on the sidewalk or off the curb again. This will give you something specific to strive for until you've got the Ollie manual so wired that you can just ride it for days. Then you can try variations like the Ollie manual to kickflip off of an element, or even the Ollie flip to manual. The options are endless.