Primary and Auxiliary Techniques
Each primary technique should have an auxiliary "back-up" technique. The primary technique will cause the most damage if it connects. If not, the auxiliary may connect. If the primary connects, the auxiliary may also connect, and may then be considered a primary technique. The auxiliary technique may also be used first to manipulate the opponent by opening the torso centerline, shifting or disrupting balance, interrupting footwork, locking, twisting, or jamming joints, or inflecting pain. Attacking a skilled opponent without first (or simultaneously) neutralizing him by applying one of these manipulations is dangerous and useless. Actually, the act of initiating the simple direct attack itself opens you to counterattack.
Sun Zi, in the "Art of War" (see Art of War topic) says to not attack a prepared and ready opponent.
"If the opponent has no gap or slack to take advantage of, how can you overcome him, even if you are well equipped? The time to go out for the attack is when the opponent is in a vulnerable position or state of being."
The secret to combat success is to coax the opponent into a vulnerable position by using auxiliary techniques.