1. Stop worrying about kills and start worrying about objectives.
You are looking at me doubtfully.
Kills happen when you have an advantage and people don’t get out of your way on the way to taking objectives. Stop chasing people and stop seeking out fights. Everybody forgets the goal of the game from time to time: destroy the nexus. It is not: get as many kills as possible.
Yes, it is fun to duel, but you could win the game without fighting a single person. Don’t believe me? Make a custom game with no opponents. The game will end when you blow up the nexus.
I think one of the biggest mistakes people make is that they become impatient and try to force fights. Nearly ever single major mistake I’ve ever witnessed in any game is likely because somebody became impatient and tried to fight when they should have backed off. I’m not saying that you should never fight, but make sure you have a clear advantage before you do. Patience is the right move nearly every time. Yes, I have made and seen other mistakes, but most of those were recoverable or took place after they had already gotten themselves killed a few times.
2. Build small advantages every moment.
Whether it is getting last hits on monsters and minions or taking down towers, you should always be getting more gold and spending it on items that make you stronger than your opponents. What is more, taking down towers also gives you more control over sections of the map. Even though I’m saying that you shouldn’t seek out fights, they are going to happen and by having a gold, vision, and tower superiority, you’ll be in a better position to win fights that break out.
3. Be aware and share.
Always keep tabs on the mini map and be aware of enemy movements, then be sure to communicate what you see to your allies. Even a simple ping may be enough to help others notice, too. I can’t count the number of times I’ve seen fights break out and an ally is not more than a quarter screen away and they have no clue it is going on. Ping them and then ping your plight.
There’s no way around it. If you don’t practice, you won’t get better. Learn a few champs exceptionally well, and play all champions at least a few times. No excuses about not having IP, either. Free campions rotate in all of the time. Play them and get to know how they work and how they are beat. You don’t have to play every champion often, but at least once or twice. Focus on really mastering a few champions that work well for the roles you like to play.