Throughout Valoran, the resolve of Demacia's military is alternatively celebrated or despised, but always respected. Their ''zero tolerance'' moral code is strictly upheld by civilians and soldiers alike. In combat, this means Demacian troops may not make excuses, flee or surrender under any cirumstance. These principles are espoused to their forces by unrivaled demagogues who lead by example. Garen, the valiant warrior who bears the title ''the Might of Demacia'', is the paradigm to which these leaders are compared. Thousands of great heroes have risen and fallen on the bloody battlefields between Demacia and its preeminent rival, Noxus. It was beneath their mighty banners of war that Garen first met steel with Katarina, the Blade Mistress. The infantrymen who beheld this event (and survived) commented that it seemed as though the two were locked in a mortal waltz against a symphony of clashing blades.

Garen, the pride of the Demacian military and leader of the Dauntless Vanguard, returned from this battle breathless for the first time in his career, though some speculate that this was due to reasons other than exhaustion. The plausibility of these rumors was bolstered when, in every instance thereafter, Garen seized the opportunity to encounter the Blade Mistress again. A paragon of Demacian ethic, Garen never entertained such allegations, for he knew others couldn't understand. Even simply the pursuit of a worthy opponent on the battlefield is, to a true warrior, the reason to rise each morning. The promise of one, particularly so beautifully and diametrically opposed, is the validation of his existence.

''The most effective way to kill an opponent is to slice through the man next to him.''
- Garen, on front line strategy

Pros:
1.Good early game killer.
2.Good passive
3.Nice damage
4.Funny crits
5.Decisive Strike can deal damage to towers.
6.Demacian Justice is a great finisher (kser).
Cons:
-Damage isn't that great late game
-Focused alot
-If you don't have Last Whisper, Armor Stacking hurts you
-Can't 1v1 well

Marks:
Armor Penetration-For those pesky tanks that are coming after you because you killed all their squishies.
Seals:
Armor-For those pesky carries that are trying to defend themselves when you are slaughtering them.
Glyphs:
For glyphs you could go two ways:
Cooldown Reduction-Garen has pretty long cooldowns so this might be a good idea.
Magic Penetration-To amplify the damage of your Demacian Justice.
Quintessences:
You could also go many ways with quints.
Armor-To protect yourself better.
Magic Penetration-To amplify your ULT further.
Armor Penetration-To increase your damage with your attacks.
and Health-To be a little less squishy.

Offense:
I typically put 21 in offense just for the improved exhaust, cooldown reduction, and attack damage. *Note: I would not get rally.*
Defense:
I would get definately armor and dodge. Then put the points in reducing damage. 9 points in defense. *Note: I would not get fortify.*
Utility
Why I would not get points in Utility.
The only things you could possibly get is:
Improved Teleport:Don't get this if your obviously not using teleport.
Reduced Death-It's kind of useless. Besides you won't ever be dead :D
Mana Regen-If you didn't know by now that Garen uses energy then you should find a new champ to play XD.
Improved Ghost-Not terrible but only get it if your using ghost.

Early Game/Mid Game/Late Game:
I would start out with boots and 3 health potions. Boots would help you get to the bush faster and the potions are for pesky harrassment delt by the carries that you will destroy later. Then I would get Frozen Mallet and a Boots of Swiftness. Then if your really racking up kills then get a Sword of the Occult. But before that I would get a bloodthirster since it's easier to get now that the price of BF sword was reduced to 1650 from 1850. I really liked that since BF sword is annoying to save up for if your not fed. By now you should be doing well and get a GhostBlade witch has a good active. Now get Phantom Dancer because it's great attack speed and crit. Mostly Garen looks ridiculous critting over and over again.
*Note: If you are not getting fed then instead of getting Sword of the Occult I would suggest getting a Spirt Visage. To increase the healing of your passive. Right now I'm not certain it will work cause I haven't tried it. But besides if it does work that would be great and it gives 10% cooldown reduction for Garen's long cooldowns.

Skilling
I would get Judgement first because it would rack up so many kills. You don't know how stupid an Akali would look sitting in her shroud at low health and you spinning away her HP.
Then get decisive strike whitch is a nice combo with judgement. Decisive Strike also gives you a good speed boost to catch up or get a away. but many catch up. >:D
I would get Courage at intervals of 4,8,12,and 18.
And of course Demacian Justice at 6,11, and 16.

Good Spells:
Ghost:To catch up or get away when the boost from decisive strike isn't enough.
Exhaust:Good when fighting another DPS champ or chasing.
Ignite:To finish off someone after a deadly Judgement or Demacian Justice.
Cleanse:It's ok if you are stun and want to chase someone or get away.
Flash:To also chase or get away.
Ok Spells:
Clairvoyance: It's O.K. to have this...maybe it's averagely useful but I would just let the support champs get it.
Fortify:It's ok for getting tower dived and protecting a tower but again I would let someone else get it.
Heal:To make someone try really hard for a kill then dying because you healed at the last second.
Rally: To give you that boost in attack damage you or your teammates need in fights.
Teleport: You could get int teamfights faster and save towers but you already have Boots of Swiftness, Ghost, and Phantom Dancers.
BIG NO-NO's
Clarity-I don't know how much times I have to stress this but Garen uses energy!!!! LOL
Revive-Not very usefull if you die then come back just to die again. o.o
Smite- Dude your not jungling. Waste of space for Garen.

Its always nice to turn on Courage then running into the teamfight with judgement. During team fights always target squishies (of course). The silence on Decisive Strike is devastating in a teamfight. Be sure to target caster with your silence (or maybe Tryndamere before he can activate his Endless Rage). When someone is low enough ULT!. And boom your team wins the fight.