These are hints to help you decipher the coverage quicker. The keyword that I want to make sure you guys understand is HINT. These hints will help you but experienced players will sometimes takeaway these hints.
These hints take place during the presnap phase of a play. For those who do not know the presnap phase of a play is BEFORE the play.
Presnap Safety Rotations
You probably have heard the term two high defense and one high/single high defense before. Well this is a hint to which coverage you could be facing.
Single high defense
Within the single high look the most effective coverage are Cover 1 Man Defense and Cover 3.
Two high defense
Within the two high look the defenses that are most effective are the 2 Man Under Man Defense, Cover 2, Cover 4, and Cover 6