Well, one thing that helps is playing the various champs when they are on the free rotation. Also keeping an eye on how each person counters which character. For example a Janna or Thresh may be used vs an enemy Leona because they can knock her out of her E (Zenith Blade, her dash incase you didnt know). This makes them a very good counter if you have good reflexes and it makes the Leona less likely to be successful. Leona can counteract this by trying to catch the Thresh/Janna off gaurd. They can do this by coming from a bush, using her Ultimate to stun before using her E to get in close etc.
There is a lot of stuff to figure out, so experience beats having it explained every time. Instead of trying to figure out what you did wrong, try figuring out what THEY did to counteract you. The game is proactive and reactive. You either start the fight or you react to the fight. Sometimes what went wrong is you should have started it, sometimes what went wrong is you didnt react fast enough, sometimes what went wrong is you did the wrong reaction......... And many more possabilities........ Most of this is based on what champions your team has and what experience you have with them and what team comp the enemy has etc.
Hopefully this gives you something to think about lol
