Step 3 — Check the box

Count defenders near the line of scrimmage. Seven or more in the box = run-first look or pressure coming; a light box (6 or fewer) = pass-first, likely nickel or dime. Linebackers walked out over slots hints zone; linebackers stacked right behind the linemen hints blitz or Cover 1.

With about 10 seconds on the play clock — after safeties and corners.