Summarize:

Basically, you will be standing parallel to the line of the Frisbee’s flight.   Your forearm and your wrist should be bent inwards.  Your shoulders should not move. Note: It is important during this step to keep your arm parallel to the ground, or the Frisbee will not fly flat and will veer off course. The Frisbee should be out of your hand by the time your arm is in this position.
Stand with the foot that corresponds to your dominant hand (the hand you will be throwing with) forward. Point your dominant shoulder in the direction you wish to throw. Turn your head the direction you wish to throw. Spread your feet shoulders length apart and bend your knees slightly. Grip the Frisbee in your dominant hand, with your thumb resting over the top of the disc, and your other four fingers. Raise your throwing arm parallel to the ground and tuck the Frisbee into your chest. Step into your throw while keeping your toes pointed perpendicular to the direction of the throw. Move your forearm and wrist outward in a quick throwing motion, while keeping your entire arm parallel to the ground, and your shoulder in place. Release (quickly) the flying disc just before your entire arm is straight and in a locked position. Repeat and practice, practice, practice!