You should at least have a basic knowledge of football. If you plan on calling all of your own plays without the help of Gameflow, you should know, for example, that an offensive package with three wide receivers calls for a nickel package so you have enough defensive backs to cover them.
On offense, it's helpful to be able to tell what kind of play the defense is running. Are the cornerbacks playing 5-10 yards off of your receivers? If so, it's probably zone coverage. Take your time and look for the open hole on defense to throw it.
Really though, you should just start playing and learning from your mistakes. Take it simple, learn what your "bread and butter" plays are going to be, and what's deep in your playbook that you'll only pull out a few times a game. Experience, after all, is the best teacher. --- But I play on PVP servers for the sole purpose of the STV levels. Damn place is like Vietnam. - Xilnold
Just do the skill trainers and play on a lower difficulty until you get a hang of the game. Once you're comfortable find a team you like and try and understand what will work for them offensively and defensively and you'll be fine. --- Ten funerals since I started high school... Life ain't always beautiful, but it's a beautiful ride...
Offense is generally easier to get a hang of than defense
Or to be more precise, you have more room for error on defensive playcalling. The "Ask Madden" playcalling is usually *ok* so if you're not sure lean on it. But try to learn the game. American Football is basically one giant game of chess and the more you know how it works the easier it is to take advantage of it --- We Americans will never take over the world. We're far too lazy. We'll outsource the task to India, and then take the credit for it. ~ Waffleman