1) Don't flame, I used to be a flamer (reformed) and since I stopped I began to climb as it stopped tilting my team and try to offer them some encouragement if they aren't playing well.
2) Don't blame others for your mistakes and take notes of them so you can improve on them.
3) Play smart, don't go for flashy plays and don't risk going for farm if you are gonna take a serious amount of damage or die to get it.
4) Try to avoid maining OP and broken champions as they will likely get banned, picked or get hit hard by the Nerf Hammer.
5) Buy control wards as they are very helpful to have extra vision and better chance of not getting killed in a gank.
6) Don't just follow build guides as they are just what you should aim for, items can be situational.
7) Try and find a friend around the same rank to duo with, for example, if you are a Bronze 5 don't look to play with someone in Silver try and find someone around Bronze 4/5 so they are around the same skill level.
8) Don't have the mentality of "I don't belong in this elo" as it will affect the way you play.