Handle Bars should sit around hip to waist height when standing on the scooter deck. The exact height is personal preference.
Those who like to do a lot of whips and park tricks tend to prefer lower heights. While in contrast the more street style riders prefer higher bars for comfort. The chart in the back of this catalogue gives the bar height measurements to help choose the right scooter.
Another consideration is deck sizing. The bigger the deck the more mcomfortable it will be for larger riders. The smaller the deck, the easier tricks will be and overall the scooter will be lighter.