Lol, I'm not pro, I still make plenty of mistakes. But I have been ranked over 1500 (1509), which makes me better than a lot of people.
Honestly, the skill in LoL comes not from how well you play your champ, but how well you play within your team. For example, let's say that you're ganking an Ezreal, you are Garen, and your buddy is Sion. It's a very difficult gank, so you need to play your cards right. If you were unskilled, you would both use Stun/Silence at the same time. Then, one of the CC's would be wasted, and Ezreal would blink away. If you were good, you would wait 1.3 seconds after Sion's stun to use silence. This prevents Ezreal from blinking, letting both of you use your comboes.
When I played with Thorns yesterday, he was Warwick, a jungling Tanky DPS. I was Swain, a Disabler and Support. WW's ultimate suppresses (a glorified stun) a target for about 2 seconds (EDIT: 1.7 exactly). Swain's W spell is an AoE root that becomes active after a 1-second delay. I would never initiate a gank with the spell, since the enemy could just get out of the delay. I would never use it as Thorns ulted, because that would waste the root. Instead I would count 1 second and then lay it down, which would stunlock the enemy.