The best thing you can do is watch people like Phylol or Redmercy on YouTube. They have a couple of videos explaining some of the more advanced things in League, for most roles too.
But if you don't feel like doing that. I'll give you a couple tips:
1: Learn every champion, and all of their abilities.
2: Learn when their power spikes are, and how to counter them.
3: LEARN TO PLAY SAFE AND NOT FEED KILLS!!!
4: Vision.
5: Team comp is important; ADC's need peel, you need an engage or two for teamfights, CC wins.
6: Thinking and instinct go hand-in-hand.
7: Practice makes perfect.
8: Don't be a hero, but don't be afraid to make the play that wins the game.
9: Learn how to play when behind.
10: Be the best Last-hitter you can. (unless you're support)
Lastly, its a team game. You can carry, but isn't it easier to play as a cohesive unit, and win that way?
Play with your team.