One thing that hasn't been mentioned is the flexing of the lower portion of the rod in this process.
The leverage for the long cast comes from the lower part of the rod (at least for me). You've got to learn how to put this lower third of the stick into play and the easiest way to do that, (again, I think), is to imagine pulling the line from behind. Imagining this will help you push your rod hand forward without bending the wrist, causing the deep "to the corks" flex in the lower, power, part of the rod. Hard stop at about 10 o'clock and a soft, pointing follow-through help get the thing launched. As has been pointed out, it doesn't take much of a pull in terms of number inches of line to get the double-hauled line rocketing out over the water.
I got this cheerful fact from the Mel Krieger book on fly casting and it certainly works for me.
Last edited by Eric; 06-14-2007 at 12:21 AM.