When your in mid lane wait into your lvl 6 to try to kill the enemy when trying to hit the enemy with Q when doing that hit the minion when there are 4 left and the enemy is close hit Q on one of the minions and it will hit the enemy champion when the enemy is low on health and you have ignite and flash and ult with full health you can turret dive in and kill the enemy

When farming with Yi if you have blue buff or alot of mana regen use Q to kill the minions its alot easyer and faster also you have are 50% chance of hitting the enemy champion