How Can I Get Better at League?

Go to Op.gg and record a game. People tend to need to see in game footage to tell you.

Turn on smart casting. Learn how to attack move (shift+right click). Look up pro player masteries and runes. Watch streams at twitch.tv

Don't ever rage or use the chat. Keep track of flash timers. Only use the chat to write down timers so if Annie flashed at the 10:00 mark, type "annie flash 1500". Ignore everyone and focus on core mechanics like last hitting, vision control, etc. watch YouTube videos. If you can sit down and watch this entire video you'll improve drastically. No fast forwards. http://youtu.be/1oPLc6DZvz8