As a few of you indicate, there is indeed an intermediate mode prior to true planing. It is when the hull is in the process of climbing up the bow wave. This takes tremendous effort, and your placement can actually affect the duration of this transition. To help the boat 'shift gears' you have to move just slightly forward while the boat is climbing the bow wave. This can take only a few seconds if it is occuring during a gust. You know the boat is climbing because you can actually see the bow rise against your horizon. Moving slightly forward, pulls the bottom of the stern out of the water, releaving that little bit of residual drag. At this moment, the character of your wake will change slightly. Its hard to describe, but essentially there is a momentary break in the pattern. The moment that has happened, the boat has successfully climbed up the bow wave, and the stern is no longer dragging. Lift the centerboard slightly to reduce drag further, and as the boat accelerates, sit just slightly back again so the the trim has her riding on the aft most portion of the hull, but without the transom dragging. If the wind is steady, you can hold a plane for a long time. Most times however, you will only get a few minutes. Steering gently to maintain the plane also helps but you really need to be able to read the slight windshifts to do this. A windex helps tremendously.
Planeing is also best accomplished with minimal weight in the boat, so that typically means sailing solo. Now you can see why it is difficult to achieve.... While sailing solo, one eye has to watch the bow rising on the horizon, while the other eye watches for a change in wake pattern. Once on the plane one eye has to maintain as straight a track as possible so that the rudder does not act as a decelerator, and another eye on the mast top windex to ensure that you maintian optimal apparent wind.
To that add one hand to adjust the jib and main, while the second raises the cb slightly..... okay okay... that's pushing it, but it is something like riding a bike... a very delicate balancing act. See this u tube video as an example
http://www.youtube.com/watch?v=QpWrEVGv ... PL&index=3