From pre Season I to now, what I have learned, a list

• Objectives are more important than kills.
• Kills are meaningless without map control or objectives.
• Farming on champions that don't scale well is slowly losing a game.
• Most AP champions don't perform as well late game.
• Pink wards are man's best friend. Green wards are strong allies.
• Missing CS does matter.
• If you have the choice of farming, or helping your team, help your team. But also if you are going to group, get your lanes pushed first. It will mean more objectives and if you're out a long time you won't give up free turrets to split pushers or minions.
• Baron is only ever a good idea if you have killed their jungler, or significant portions of their team are bottom lane farming and you have vision control.
• Dragon control wins games.
• Jungler's have the most game impact.
• Defensive buys beat offensive buys in gold per stat and duels, but offensive buys are able to secure kills that defensive buys aren't, and make bigger game impact.
• There is no ultimate bulid. You adjust your buys to the game at hand for every champion.
• Farming isn't a very efficient way to get ahead, especially in higher ELO where people are able to get near perfect CS scores even while pressured. It as most keeps you in the game, out playing yoru opponent and getting other lanes ahead while not losing CS is your main objective.
• Support is actually the strongest role in the game. And people don't know how to play it or discriminate against it or fail to understand why it is the most strong role in the game so it is an easy way to climb in rank.
• There are no easy wins. You have to play to your full ability all game every game or suffer the consequence of your laziness.
• Wards create opportunities. Good players harvest opportunities but even bad players can be prevented from doing something bad with proper vision.
• Being positive in a calm way tends to make your team more focused.
• Being a team player makes people want to win.
• 3v5s are winnable if you are able to use the other teams confidence against them and never stop pressuring. But without waveclear you're doomed.
• Waveclear means you can roam, roaming means you can get other lanes ahead. Punish champions without waveclear but be careful not to set yourself up for a jungler gank in the process.
• You're probably either a lot worse or a lot better than you give yourself credit for, but ranked is a good way to find out. (I used to think I was one of the worlds top kat players, maybe in pre season I, I was but I doubt it no matter how good you are there is someone better).
• Learning from other players is a form of social learning and not to be undervalued or scoffed at. But neither should you neglet putting yourself into your champion playstyles and builds.
• You can't just farm better, and get a few kills and a turret and expect to win even 50% of your games. It takes a lot more than that, game knowledge, and helping other lanes get ahead is how you ensure victory.
• You won't think like every person you run into.
• Mechanics aren't as important as teamwork or game knowledge but can be an edge in close fights and crucial for a few champs/roles but overall baseline mechanics with greater game knowledge is far more valuable.
• Learn to be good at every role and you will be better at the role of your choice.
• Play all your matchups at least 30 games, once you get your butt kicked as them you can know how to kick their butt.
• Try to keep your roster small. There's always more you can learn even with the champion you play.
• The game changes frequently, adaptability is as important or more important than experience.
• Mobility and how to execute it can make amazing plays, or make you die stupidly so use at your own caution.
• Skillshots don't actually take alot of skill, but can take good mind gaming.
• Quickcasting is pretty essential for sound mechanics. (Ahri R -> W -> 1 (for dfg) -> E -> Q -> Ignite (F for me) try doing that combo without quickcast in the time it takes one of Ahri's dashes to complete without quickcast).
• Bob is a unicorn.

I'm sure there's more but I just felt like making this list, hope someone can get something from it have a nice day :)