Garen is probably one of the best champions in LoL. Garen is an old champion and and is very beast. My way is building tanky but plenty of damage to shred your enemy into piecies. Garen is so good in the fact that he has NO Mana. So you dont have to worry about when to use your abilites. Only thing is cooldown and unlike Mordekaiser and Dr. Mundo, Garen abilites dont cost health. His passive is one of the best with a regen of health when not in combat for 7 seconds. His ult is my favorite because it finishes off enemies when they have like 400 and below health.

Well to tell you the truth, the runes you see are very commonly used for any ad champion. They provide armor pentration, more armor, and magic resist which makes you unstoppable.

I choose 9/21/0. It proves good starting damage and proves good defense early game. It will also help in the long when you need that extra health regen or armor.

I choose mecury trends because it helps when garen gets slowed alot. Get Aegis because it gives armor and damage to allies. Then sunfire cape because your close to the enemy and that damage per second can really help when 1v1. All adds to the armor. Then go right to Force of Nature because it gives health regen and greatly increases magic resist. It adds a nice balance of armor and magic resist. At this point it is really hard for you to die and you can do your E usually 2 times before they retreat. Then start with damage. Get Frozen Mallet to add even more slow. They cant go anywhere at that point. Your abilites ans mallet are a perfect combo to slow the enemy down enough to pick up the kill! Then last is atmas because it gives armor and armor pen which is really well fit for Garen. You should be getting feed and the game will end with a surrender. Last is just the elxir because of full build so it helps you reach yor max. Get blue elxir if you want cooldown reduction:)

You want to max you E by level 9. Your E is Garen's main damage and can deal lots to an enemy because of per second damage. Then Start to max your Q by level 13 because its good to silence them so they cant do anything and you can have a head start. Last is your W which is only good for running away or when Q,E,r are on cooldown. Then make sure you get R when ever you can.

I pick ignite just in case your in 1v1 and you feel like you might lose or you can pick up a kill if enemy is running away. Garen is not that fast. Then Flash because you can use it aggressivly and defense. To escape or to get ahead of your enemy. You could use exhaust if you want extra slow but really dont need it. Could use ghost to catch up to your enemy or to get away. Anything else is just not good with Garen.

Pros
1 He is great at farming
2 He is very tanky and deals great damage
3 His ULT can kill champion quickly if low health
4 His passive is great throughout the game
5 He has silence, slow, and shield as skills!
6 He does not have mana. Stress solver
7 Can use skills to escape if needed
Cons
1 If not great early game tends to fall of late game
2 Cooldown on ultimate can kill
3 Not fast enough
4 Depends on items early game to do well
5 His passive on his W is a waste doesn't do much; cap is 25
6 His silence sometimes can land on minion enstead of your enemy

when fighting use q to silence then e to slow. Then w for shield then once e is ready again hit e. After that hit R and that should kill them. Cooldowns and really have an impact on Garen so try to get a teammate to help you out. Ignite if after use q,e,r if still alive. But with the build they should be slowed where Garens skill are off cooldown and can start the slow again. Also try to avoid range champions when by youself and dont engage untill you know you have back up comming.