"Stand diagonally from the turret to maximize your harassing range"Realizing that this might not be a tip that everyone knows about, it gives me a good opportunity to take some screenshots to show you how it works! (Click on any of the screenshots below to zoom in)
Mid Lane Positioning
When I say "stand diagonally" from the turret, I mean in relation to the lane itself. In the first screenshot, I'm standing directly parallel from the turret in its maximum aggro range. You'll notice that it has an orange border around the turret when it's targeting me (they've also added a pinging sound, which makes it easier).
Standing straight against the turret
Meanwhile, in this second screenshot, I'm standing off to one side, which means that I'm almost twice as close in terms of the axis of the lane, but I'm just out of turret range because of the way lines work. The closest path between two points is a straight line, which means that the more diagonal you are, the closer to the enemy side you can get without pulling turret aggro. (Math buffs let me know if I should phrase that differently.)
Standing diagonally from turret
The reason why this is so effective, is that I've annotated with an "X" where an enemy champion would like to stand while CSing, which is as far away from the enemy champion as possible without taking free harass.
However, because of the way the creeps line themselves up, he or she is forced to stand in the area marked with a circle to last hit all the creeps or get pinned against the turret. This means that as long as you move in and out right after your auto attack releases, if they try and last hit under the turret it's free harass all day long without ever pulling turret aggro.
Enemy positioning locations
As you can probably tell, if you were standing in the same spot as in the first screenshot, harassing them without pulling turret aggro would be quite difficult as they can stand even further off to the left side to CS and pull you even deeper into turret range.
Naturally, the best usage of this would be bot lane where there's always a strong ranged AD carry that benefits greatly from the poke range, e.g. Caitlyn. Be cautious though, if you're using this tactic stay away from Alistar and Vayne, who will chain CC the living daylights out of you if you get this close to the wall, after which you'll come back and say "Nerfplz told me Caitlyn counters Vayne, and that I should stand near this wall..." I did no such thing...
Bot lane parallel aggro range
Bot lane diagonal just out of aggro range (no need to get this close)
The best champion to use this on would be on someone like Ezreal, who can benefit greatly from the poking and positioning himself for solid Q shots (which you might do unconsciously anyway because of the way the creeps line up).
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