The double haul is seen by the flyfishing world as the pinnacle of achievement in casting skill. As people try to cross this casting hurdle, they find that coordination, timing and hard work are prerequisites. Mistakes come from making too long of a pull, really ripping at it. Your pulls should be in synch with your casting stroke and be of the same approximate length. Short strokes mean short pulls.
Long strokes mean long pulls.
Try this in practice. A second mistake is to make your downward pull without returning your line hand to a position near your rod hand. This leaves your line hand in the wrong place and either results in awkward, weak pulls or injects killing slack into the cast. Practice exercises To reach the advanced level of casting 75 feet or to overcome heavy wind, you must double haul. Pick up your line with a single haul to the rear and do not release line into a rearward shoot.