I didn't watch any streams or anything, but I'm sure they are very helpful. However, I just learned through consistent practice in normal head to head. Scheme is important, and defense is all important. Offensively, I'm not superb: I just run the ball and throw a couple of slants or streaks out of bunch formations. Defensively, always look at the personnel your opponent is coming out with so you're not at a mismatch in your defensive set, pass commit when you know your opponent is passing, and learn tendencies both in each game and overall as you play. The last one is crucial, because as you probably notice, a lot of people like throwing over the middle, or throwing slants. To go along with that, people also like calling certain plays on 3rd and 4th down scenarios. There are patterns that you'll notice amongst players across the lower to mid skill levels. The key is to know how to shut down the middle: pass commit inside, user a linebacker over the middle. Usering the linebacker is key because it forces the individual to second guess himself, and also if he locks in on receivers he'll absolutely mess up. As long as you're holding triangle, you'll get an instant pick if you're following his favorite route. For example, people love throwing four verticals whenever they're in a bind. I follow their tight end the whole route until they throw it, and it's an easy user pick. Now, obviously shutting down passes over the middle isn't this simple, and you're going to learn how to adapt to different scenarios as you move up in skill level, as people will generally know how to throw passes other than slants. This is where your experience culminates; it's a mind game. You have to goad your opponent. I like to play very loose and passive to start off games, to see what they like to throw at me, so that later on, I can press down on their tendencies and force them to change. If they do, it pushes them out of their comfort zone. If they don't, well, mistakes will be made. One other thing, knowing your own tendencies goes a long way in not only bettering yourself, but understanding your opponents. The things that I look for in my opponent, are very often what people exploited in my game or what they could have exploited before I realized I needed to adjust. I know this is very broad, but it is simply meant to be a foundation for the way you go about your game.
tldr; Defense. Pay attention to patterns in your opponent's game. User the linebacker.