Freezing lane- Keep your minions close to your turret, doing this by simply only last hitting minions. If the enemy recalls and you want to recall soon after to shop, leave the enemy caster minions behind, sacrifice those caster minions, so that the minion wave will remain close to your turret. If your opponent does not have teleport, you can instead push up the wave all the way up to their turret.
Teleport Usage- For most of the first 15 minutes of the game, you'll want to use your teleport to go back to lane and farm. Once mid-game hits, you can leave and start helping your team with objectives (dragon, baron, turrets, etc.)
Proper usage of your kit- In teamfights, you want to wither the adc, or just generally who ever does the most damage, the wither slows them increasing over time and reduces attack speed, so if you have frozen heart aswell, it will have a huge affect on their attack speed.
FARMING- Always farm to your best, but don't make your lane push, last hit as best as you can with your Q to get maximum stacks. you want to be getting 20-30 stacks a minute.
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