From The Martial Arts Encyclopedia

This list will contain the most commonly used excuses and tactics for avoiding a challenge or Gong Sau disingenuously. These are usually employed in an attempt for the individual to save face within their group of supporters, even if it is transparent to everyone else.

Obviously the easiest method of avoiding a challenge would be to simply decline to participate and provide a valid reason. This is a compilation of invalid reasons, excuses, and tactics used by those who have no intention of actually demonstrating their fighting ability, yet want to be considered as reputable on that ability.

Many, if not all of these have been demonstrated on various Martial Arts forums, including and especially Bullshido.net.

#1. Raising the Stakes

In this method, the challenged takes it upon him or herself to alter the terms of the challenge to an extreme beyond which any reasonable person would not participate in an effort to claim victory by default and make the other individual out to be a coward.

An example of this would be thus:

Individual A challenged Individual B to a kickboxing match over a dispute on striking skills. Individual B, realizing that he or she realistically stands no chance, attempts to alter the terms of the challenge to "no rules" and hints at or even explicitly states that they will use biting, eye gouging, or weapons.