thinking your plays is the main determinant of success or failure in your sport (Jimmy’s and Joe’s)

copying plays from other teams or video games, because somebody else had success with it

too complicated for your athletes to understand every signal

too complicated for your signal callers

too much practice time needed to make each play work

too many plays

too much emphasis on disguising the signal call for the opponent. Do this only when you find out the opposition knows what’s coming)

Teaching your playbook by only tossing it to the athletes telling them to read it. Sounds ridiculous, but happens all the time.

Being careless about the verbiage you use while teaching

changing or adding plays throughout the season because they don’t seem to work

running the plays “on air” (without an opponent) to test them. They work well, and break down once opposing players are present