*5. Decision making. What seperates someone from 1500-2k elo is not mechanics or last hitting it's mosty making bad decision as to where someone who is truly 2k will make a lot less of them. When you die to something stupid try and figure out why. Know when your character is strong - early, mid or late and abuse that part of the game.
Most players at 1200+ ELO will know how to play the game, will know how to handle the champion they like playing, and will be decent at last hitting. The biggest cause of loss of games, especially at around 1400 ELO is throwing or becoming overly confident. I've lost more games where we had better team comp or were ahead simply because one person got caught or dived too hard, than anything else. I've also won a lot of games that were horrible for us at first but once the team stopped chasing around the AP Yi and focused the other players we won every team fight.
So know when to back off, know when to go in, and where to position yourself to avoid certain things. Don't be negative, but don't be afraid to yell at your team and tell them to stop letting themselves be kited. Don't let the bad Vayne who is under leveled and has the worst score in the game lead your team with a yell to "PUSH!" when they are out leveling us and have Baron, let her die alone if she wants to be bad, don't stay near her and thus snowball the bad decision making.
In short, remember, Bots have perfect timing and amazing map awareness, what they don't have is good decision making. They will combo and last hit like pros, they'll never outplay you though and that's what's important to remember when playing this game, you're not going to magically own the enemy in Rambo mode, you'll win through small advantages here and there. Take your victories and don't over extend.
Edit: Also remember to go up from 1350 to 1400, is roughly 5 wins with 0 losses, or some ratio of 6:1 wins:losses. That's just how tight you have to play. My current record is 79 wins and 65 losses, that's +14 wins I had to gain without a single loss.
At some point +14 wins isn't going to be a big number, but at the small number of games I've played, it's a big percent.