When you have a top spinning in your hand, you can prolong its spin a little bit by correcting it when it starts to tip. The trick is to make small counter-clockwise circles with your hand. More specifically, you want to "follow" the top's tip. When the top tips to the right, the tip points to the left; move your hand to the left. The tip will then go around and point toward you; move your hand toward you. By making circles that "follow" the tip, you can straighten the top again very quickly. A similar method is used when bringing the top back up from a trapeze.

Hand Balancing Video