Garen

Strengths

Garen's regeneration greatly increases if he can avoid receiving damage for several seconds.
Judgment deals maximum damage when only hitting a single target. For effective trading, try to position such that only the enemy champion is hit.
Garen is only constrained by cooldowns, making items such as Black Cleaver very effective for him.

Passive · Perseverance — If Garen has not recently been struck by damage or enemy abilities, he regenerates a percentage of his total health each second.
Q · Decisive Strike — Garen gains a burst of Move Speed, breaking free of all slows affecting him. His next attack strikes a vital area of his foe, dealing bonus damage and silencing them.
W · Courage — Garen passively increases his Armor and Magic Resist by killing enemies. He may also activate this ability to give him a shield and tenacity for a brief moment followed by a lesser amount of damage reduction for a longer duration.
E · Judgment — Garen rapidly spins his sword around his body, dealing physical damage to nearby enemies.
Ultimate · Demacian Justice — Garen calls upon the might of Demacia to attempt to execute an enemy champion.

A suggested 5-lane lineup built around Garen, based on hero partnerships and role synergy — not win rate.