Find a player significantly better than you (Go with at least gold, preferably higher), get on voice chat with them, and have them 1v1 you. Not to prove dominance. Not to kill you. But so they can see what you are doing in lane and tweak what you're doing. They can give you advice on zone control, how to time your last hits, all that good stuff. Stuff that can't be explained fast enough in chat.
After than, play a bunch of Normal Draft games (Or Teambuilder if you want to practice a specific champion in a specific spot) and try to put into use what you learned. Rather than just grind games, stop after every game and think about exactly what you could have done better, write it down on a sticky note, and slap it down next to you so next game you remember what to focus on. Then stop worrying about everything else in the game, and just get that one aspect up to the level you want it. Sometimes it is really hard to focus on one thing with an entire game going on around you. So you can even do stuff like making a custom game on Rift against a bot (Or even without a bot) and just practice farming. Do it until you can get every minion every wave without issues. Add in a bot, get every minion every wave. Repeat until you are comfortable and don't even have to think about it.
This is how training for pretty much every sport and game is done. Focus on a specific thing, starting from the easiest version, and slowly work it up to harder. Then incorporate it into the game. Just playing a ton will eventually get you there, but specific practice makes that way faster.