This build for Garen is very similar to DEWO's build; I changed the masteries and items only slightly. Once you get to the Sunfire Cape, you must choose between it and buying Force of Nature. Choose based on what the other team is focusing on (i.e. Choose Force of Nature if other team is mostly casters). Other than that, simply use Judgement to deal good damage and use Decisive Strike to silence. Early game you can keep the other team pressured well if you have a half-way decent lane partner. If you are at half health or above, depend on your passive to restore health, but if your health is low use a potion or port back to base. Also, I use Exhaust and Ghost as my summoner spells because they allow you to catch people running away and effectively run away yourself.

Thanks for reading!

-GhettoChipmunk