When casting a flyrod, in most cases, tight loops will allow the fly to travel farther, more accurately, and with less effort. To cast these tight loops, the tip of the rod must travel in a straight line path, slack must be eliminated, and there must be a constant acceleration to a sudden stop. The most common mistake is using the wrist to move the rod which causes the tip to travel in a half circle or windshield wiper type motion.
Beginning anglers should start with approximately 20-30 feet of line outside the tip, a leader of at least 7 feet and a small piece of yarn on the end. The color enhanced video below shows a basic fly cast in both regular and slow motion. In this case, the straight line path of the rod tip is up in the back and down in the front so the forward loop unrolls right above the target. Casting in a level plane will cause the front loop to straighten high above the water and can be blown off course by the wind.
Watch as the rod constantly accelerates and the weight of the line cause the rod to bend. The sudden stop cause the tip to straighten and helps to form the loop.