Hi, I'm Elite102396, and this is going to be my first guide. I see a lot of people playing Garen as an offtank, and even some as full on tank. I personally think that this is a HORRIBLE way to play Garen. Look at his AD ratios on his abilities, and then look at the potential damage it could do with a Garen at full build. That's why I'm here to give you a guide on Garen as a full-on AD Melee Carry. In a 1v1, I believe that if you play him right, he can dominate ANYONE. By level 6, you should have all of your abilities, and then you will become real scary, real fast. Q-->E-->Autoattack-->R. GG.

Pros:

A killer
Has a 2.5 second silence
His spin and his decisive strike do an insane amount of damage
He's a great ganker
He's one of the funnest champs to play, imo.
He doesn't run on mana, so his abilities are only restrained by cooldowns
He's great at regenerating health, because of his passive


Cons:

With this build, he has a decent amount of armor and MR, but he's still pretty squishy
He's really item dependent, because without stacks of AD, his ratios won't be utilized at their full potential
He's squishy
You're not a tank
Did I mention he's squishy?

Ok.
For runes, I go with 9 Marks of Desolation. These give you an insane amount of armor penetration...around 15 armor penetration at level 1. This will help you kill extremely easily.