Garen vs Gragas

Trade with Decisive Strike (Q), then Judgment (E), and back off: the Decisive Strike silence stops your opponent from answering with spells.

During Judgment (E), stay closer to your opponent than to their minions: the nearest enemy takes extra damage.

After a trade, back off until Perseverance (passive) kicks in: without recent damage taken, you regenerate part of your health every second.

Activate Courage (W) just before the bulk of the damage: you first gain a shield and tenacity, then a longer damage reduction.

Save Demacian Justice (R) to finish: its true damage grows with the target's missing health.

Stay behind your minions: Body Slam (E) stops on the first enemy it meets, minions included.

Get out of the Barrel Roll (Q) area right away: the longer the barrel sits on the ground, the more its explosion hurts and slows.

Step up when Body Slam (E) hits nobody: its cooldown isn't reduced and stays at 14 to 12 seconds.

Spread out from your allies: Explosive Cask (R) knocks every enemy away from the impact, which can split you up or send you toward his team.