Hecarim vs Rammus

Cast Devastating Charge (E) far from your target: the longer the run, the farther the knockback and the harder the hit, and Warpath (passive) turns your bonus move speed into AD.

Cast Onslaught of Shadows (R) from range: the fear from the shockwave, at the end of the dash, lasts longer after a long run.

In teamfights, recast Rampage (Q) as soon as it's back: each cast that hits adds a stack, which lowers its cooldown and raises its damage.

Activate Spirit of Dread (W) in the middle of the enemies: you gain armor and magic resist, and heal for part of the damage you and your team deal to them.

Stay behind your minions: Powerball (Q) stops on the first enemy it collides with, minions included.

If you deal magic damage, lean on it in trades when Defensive Ball Curl (W) is on cooldown: without it, his resistances drop to those of an ordinary tank.

If you're ranged, don't let him reach melee range when Frenzying Taunt (E) is ready: its range is short, and it forces you to attack him.

Get out of the Soaring Slam (R) area fast: aftershocks repeat the slow there, and if cast during Powerball (Q), it adds a knock-up in the center.

Don't attack during Defensive Ball Curl (W): each auto returns magic damage to you, and he gains armor and magic resist.