Here's some tips for playing specific role to leave elo hell, at least, for me, it's enough to go above 1250

AD carry
Stay back, stay back, stay back, stay back, stay back X 10000
Hit whoever u can hit, u dont' need to focus, you survive, u do output
10 sec 100dps = 1000dmg > 1 sec 500 dps = 500dmg
Get heal, flash, kite, no need to take ignite, ignite's range is short you can't use it in team fight. If you play Ezreal, or graves, use your ulti asap. The method of protecting your teammate as an adc is simple: Kill and do output, WITHOUT DEATH.
And, always remember, no one will protect you, if your support or fighter would try to protect you, they won't be in elo hell, it's simple, just don't enter the fight too early.

AP carry
Kill their AP mid, if u can't do it, don't play. Because you want to get out of elo hell, you have to prove you are better then those elo hell players. If you can't kill, or u can't carry, then u worth staying in elo hell

Jungler
Guard dragon (No.1 important), call dragon, brave enough to dive turret if possible to kill.

Support
Ward well. Ward all entrances of jungle. And focus one of the 4 zones of jungle to ward (Ex: your own bot jungle), call mia and dragon or baron for team. Pink ward dragon and baron. Don't kill, remember, if you keep dying, at last you worth only 15 gold, without any kill, u could go tank dmg without any cost indeed. When I play taric, i always feed like a boss, like 0 10 2X. But i win the game. I just keep typing to my team, "Don't try to save me, I worth only 15 gold, let them kill me".

Top
Handle the timing of leave top to help your team well. Example : your team winning laning phase hard, dont' leave top, keep pushing and prolong the laning phase.

The most important concept is, if you can't win your lane, ask yourself a question, if you really are good, why can't you win your lane. Don't underestimate the snowball effect.
As an adc, when I lost I always speak to myself, if I got 20 cs more, and I might be able to complete my PD, then the situation of the team fight might be totally different.
Only facing your true ability and admit that you are not good could improve yourself.
The most important, but most difficult thing to get out of elo hell is, to admit that you are not that good, you are a elo hell player.
Then you will start to improve yourself a lot, then finally you wont' be in elo hell anymore

Thanks for all of your comments. I think i should correct some of my points.
Since this guide is base on my own experience, I really have to clarify that, as I said before, it works for me,but at the same time, there should be a lot of other methods to win. So, for the AP mid part, i would correct it to:
If i think i can't win my opponent's mid, I simply won't go mid

there is no elo hell i proved this when i got from 650 to 1331 you just belong where you are since your not good enough yet