I am level 12, after playing numerous games with level 30's, because of the failed match making system, I have witnessed that even level 30's, which would mean they have played at least 200 games (yes?) have learned ABSOLUTELY NOTHING.
Basic Strategies people should have learned on their way to level 30:
1. When you have given your lane 3 kills, hence: started feeding the other team. DO NOT CHARGE IN, thinking you can kill them, just because they have under half life.
2. When you are getting pushed all the way to your base , and your final row of towers: Stay near the tower, DO NOT RUN OUTSIDE by yourself.
3. When the other team is all MIA, (please look at the mini map. If there are no enemy players, it means they are all MIA). Do not push a lane by yourself and try to take down a tower.
4. (this is for Poppy, because she is a new champion) *can also be applicable to alistar, and tristana* DO NOT SHOVE ENEMY PLAYERS AWAY FROM YOUR CHASING TEAM. Even if you THINK you can kill them, unless you are the only one chasing, DO NOT shove them away. I have seem so many people do this, just after i have cast exhaust, some dumb ass Poppy will push them away to safety.
5. DO NOT TOWER CHARGE. unless your team is with you. and by team I do not mean just 1 other person. Unless You clearly know what you are doing, have a flash for back up. have a shield ready, etc. DO NOT TOWER CHARGE, just trying to get 1 kill. because, most likely, you'll die. and keep feeding.
This post is not for everyone; this post is directed at those level 30's who I have played with who have not learned even basic strategy in this game.