Wanted to share something that has been working for me lately.
Before we start, a little disclaimer: I am just a 2.4k scrub, but I am steadily improving. Dotabuff for reference:http://www.dotabuff.com/players/175780955/
I was stuck in the 1.4k bracket for a long time until I started applying what I have learned in 13 years of martial arts training. As follows, I will list the main points.
1. Be better than you were last game
This might seem like a no-brainer, but hear me out. If you truly want to improve and climb MMR, you can not think about how other players are better than you, or how you should farm like Arteezy (although it's good to watch pro matches for tips). You need to focus on YOUR game and how you can do something better than last game. Adopt the mentality that the goal is to be better than you were last game, not better than your friends or who ever.
2. Acknowledge your mistakes
It has been said a hundred times, but I will say it again. YOU are the reason you are at your MMR. I belong in 2k (at least for now) and you belong in your bracket. It might hurt your ego to hear this, but you need to internalize that. Once you admit that you make mistakes, then you can start improving on them. This leads me to the next point.
3. Let go of your ego
As in martial arts, so in DotA. Ego stops you from improving, because you are convinced that you are the best player on your team even before queuing. Let go of your ego, it stops you from learning. You are just as bad/good as everyone else in your team (with the exception of people who grief).
4. Everything is a learning opportunity
Every player has something they do well, the same applies to your teammates. Maybe the AM on your team is really good at deciding when to fight. Maybe that Lich knows every stacking timing by heart. Once you have let go of your ego and improved your mentality, you will see that others have things to teach you. I can already see comments along the lines: "My carry is 0/14/2, what can I possibly learn from them?" You can learn what NOT to do. Look at their positioning and keep it in mind, so you can avoid the same mistakes in your plays. Why learn from your own mistakes, if you can save yourself the pain and learn from the mistakes of others?
5. Keep the flaming to a minimum
This is the point I have the most trouble with personally. I try to improve on it because, the more you flame, the more others will flame. The more everyone flames, the less time they spend thinking about the game. The less time they spend thinking about the game the less time they spend playing it and so on and so on. Flaming is not constructive. That 0/4/2 Slark is not gonna play better because you told him you fucked his mother. There is a saying in my language that roughly translates to:
"One can see the splinter in someone else's eye, but not the log in their own eye."
Keep that in mind, and if you still feel like pointing out someone's mistakes, try to be constructive. Example:
Bad: "Stop fucking feeding you cunt"
Good: "The enemy is in our jungle, don't farm there"
Think on these points and your MMR will increase, and you will at least reach the MMR your skill would really put you at. From there on, it becomes more about mechanical skills, but changing the mentality is the first step.
Good Luck and Have Fun!
Be better than yourself, not others. Lose your ego. Learn from the mistakes of others. Don't flame.