The offensive formation many times can tell you if they are going to pass or run the football. The formation can also tell you what side of the field the play might be run. Offenses use extra wide receivers when they need to pass the ball, or extra blockers and running backs when they need to run the ball. Teams use different strategies to try and score. Some teams like to run the ball more than pass.
Some teams prefer to pass.
This all depends on the type of players a team has and the style of play the coach like to use. The defense uses ends , tackles and nose guards to stop the run. Linebackers help in runs and passes. Cornerbacks try to stop passes. The strong safety helps against passes and runs.