Hello everyone!
I´m going to show you how to play Garen a little different but very effective.

early game:
You start with Dorans Blade and try to do First Blood.
Trust me that will work you just have to go into the bushes. When there are already
champs in it go for it and use Judgement they will be pretty low than try to kill them if you cant use Flash to escape and start laning as usually. When you have your Boots and your Zeal you should be over the top and shouls kill any carry with your Judgement.

Mid game:
You should now have your Boots of Swiftness and a bit of your youmuu`s Ghostblade At this point try to Gank as often as you can but dont get greedy your life isn't very high! Just camp in the bushes and kill everyone who walks by.

Late Game:
Now you build should include your youmuu`s Ghostblade and the infinity edge now go as fast as you can for frozen mallet because you have a little less life as usual. try to fight with an carry with you cause you biggest use ingame is in the early and midgame. In lategame you are not doing as much dmg as the other but you can support quite nice with your silence and your ult.

You should start with Judgementcause in the early game it does tons of dmg. Then skill deceisive Strike to follow your opponents and come close enough for Judgement. Skill the rest when you want to except your ult. Skill it at 6-11-16.

Pro:

-High Damage
-Strong early and mid game
-Fast
-usefull to kill strong feeded champs in early/mid
Con:

- Low Life
- Need skill to play
- Weak in Lategame