On the very first series of the football game would you run or pass the football? Do you script your plays or do you randomly call plays based on what you see or what is presented to you by the defense?
I think that most offensive coordinator's have their own personal philosophy on how they begin their play selection in that opening series. Probably, the play selection on the fist series of the game would reflect what your plan is coming into the game and what you already determined in you scouting and game planning. If you want to establish the running game, probably this would reflect in your play calling in your first series of the football game. You've scouted the defense and determined that you believe you can run the football against them so why not test the waters and see how things look inside. A big gain on the first play would indicate that you've done your homework!
Most times if they run big on that first play you know that a second run is coming. The game now begins to unfold as the defense adjusts to stop the run. A lot of times, once a offensive co-ordinator gets you on your heels they try and stay one play ahead of you. In other words while your adjusting to stop the inside run they're looking at exploiting you somewhere else. I find that this is more "old school" and is a very effective way to co-ordinate an offense.
Scripting plays is also an effective way to play calling.
A lot of college and NFL coaches script their plays and have already determined in the game planning stage of what play they will call for a particular situation and have it marked on their play selection chart. For instance, if they find themselves in a third down and inches situation, they'll check their play selection chart and under the heading third and inches they would have already determined what plays to call for that situation and select one of the plays. Again, the play selection would be based on the scouting report.
Scripting can make play calling decisions a little easier as you have already determined in the comfort of your office with no pressure what plays to call for each situation. It also allows you to spread the football around to different players and attack different parts of the field and can take the predictability out of your play selections. The downfalls to scripting is that when things go bad you soon revert back to the "old school" way of play selections.