Hi there, I'm Cupiter and I'll be sharing some tips on how to succeed in League of Legends. This guide will be useful mostly to those of you who play a lot of games and do so in a competitive manner, those of you looking to enjoy League casually should already be doing the things I will mention.
1. Take care of your body when playing.
Don't pull all-nighters trying to achieve a net win per day at ranked. Set limits or you will be unhappy and at your computer forever. Remember to eat your three meals per day, get your right amount of sleep. Humans generally get more irritable when they are underfed and not well rested. You won't function as well, you will rage more at your teammates, and you won't notice your own mistakes.
2. Keep your rude comments to yourself
It does not help you do better, it does not help your teammates do better to say anything with the purpose of hurting the other player. There is nothing to be gained from raging at a guy doing poorly. People will have their bad games. You will have your bad games and won't want someone complaining about your poor score when you're trying your best.
3. Stay positive no matter what
This does not mean to never surrender. Obviously surrender if you feel like it's wasting your time. But in the case of a disconnected teammate, don't rage and go afk at spawn. Be supportive, play safely. If your ally decides to quit, keep a level head and report him later. He's gone, he can't hear you, and no matter how you react to it, you won't affect him in any way. If someone's calling you out in chat, odds are he just wants to see you rage. Don't give him the satisfaction and just ignore him, calm and cool.
4. Play who you're good with
If you are playing ranked and people keep calling roles, and you get forced into a role you are terrible with, absolutely terrible with... Don't play it. Ask to trade roles, just keep pressuring them and warning them how bad you are at it. That being said, not every team will be perfect and allow you to have your favorite role, so learn at least two roles very well before trying to play competitively. This also applies to champions. Forget about countering picks when you don't know how to play the champion that counters your enemy. Half of the "counters" are just skill matchups in which the countering champion has a slight advantage. If you're not good with that champion, it would still be better and more effective to play who you are used to and played a million times.
5. Trust your teammates
The most important thing ever in a team based game- trust your teammates. Trust that when they run into the enemy, they have a plan and need you to back them up. Trust that as long as you maintain your positive attitude, play reasonably well, and continue to do so throughout the entire game, your teammates will stay positive, play reasonably well, and win. Trust that when your teammates say they aren't ready to start a fight, not to start a fight. If they tell you not to move forward near that bush, trust that they know something you don't (at the very least check the bush with a long range skill to be safe).
I know I'm not the best league player and I don't even do all of these things at once. But I've found in the games where I do the most of these in, I win more often, and the players who do these things tend to carry their team more often.