This is a modest guide on how I think Garen should fit into a game (Off-tank/AD). I like playing with this build and I hope after you give it a shot, you'll fall in love with it too.

This build is focusing on defense, AD, and Armor Pen. No attack speed, no crit, no CDR. I did this because his Q is based on his bonus attack damage. That damage is done via physical damage, so getting armor pen will make this really hurt when you've got some AD to beef it up. There's no room to buy attack speed or CDR, but I feel it's not really needed for this build when there are elixirs and buffs you can get to help make up for it.

As with any other guide on this site, productive criticism is welcomed, be it good or bad.

For this build, the Pro's & Con's are as follows:

Pros:
-Well balanced between HP/AD/Armor/Mres
-Good speed
-Moderately strong defense
-Decent steady damage
-Wriggles Lantern's Wards
-Fast creep farming to maximize your W's passive quickly (+gold) (once you have Madred's)
-Strong map control w/ Teleport
-CC via the Frozen Mallet

Cons:
-Not as strong as pure damage builds
-Not as durable as pure tank builds
-Suffers from long cool downs without elixirs or blue buff
-Slow farming until the Madred's Razors is complete
-Slow attack speed

Here's what I picked and why.

Offense:
(Deadliness) Crit Chance adds damage to your E (obvious choice)
(Cripple) I use Exhaust with Garen, so it has synergy with this build (Armor Pen)
(Sorcery) Garen is a CD only champ, any reduction is gladly welcomed
(Sunder) Again, synergy with this build (Armor Pen)

Defense:
(Resistance) Coupled with my rune setup I start with 19 extra MRes (Almost = to a Null Magic Mantle, free - Obvious tank/off tank choice)
(Hardiness) Same as above, but with armor as well (+19 Armor - Cloth armor only gives 18, and you get this for free.)
(Evasion) It's insignificant, but it's better then not having dodge at all.
(Nimbleness) Your Q is your escape, this build doesn't focus on CDR, this is a big help to off-set that.
(Harden Skin) Needed a point somewhere so I could reach Tier 4, best choice.
(Veteran's Scars) 48 HP is gladly welcomed.

Support:
(Good Hands) You're an off-tank / AD hybrid, good chance you're going to die, may as well be in good hands. :P

"Cookie Cutter" start for Garen (Boots of speed + 3 HP pots).

Boots of Swiftness - Nearly all Garen's use these, there's a reason for it.

Ruby Crystal - Boost to HP for mid-game is mandatory or you risk being focused for being squishy. No one on your team wants to see a squishy Garen.

Wriggles Lantern - Gives armor (need this), damage (need this too), life steal (always good), a passive that helps build your W's passive, and an active that I personally love (Free wards!)

Aegis of the Legion - A balanced way to make you more beefy, and with this build, we're all about balance. (You've already got the Ruby Crystal, so it's cheap...er.)

Pickaxe - Small boost to your damage (First piece of Last Whisper)

Giant's Belt - More health! More tank-like. (First piece of Frozen Mallet)

Phage - Even more health along with a small damage boost and a chance at some CC (2nd part of Frozen Mallet)

Last Whisper - Getting this item should show a good jump in your damage, and make your Q hit for surprising amounts.

Frozen Mallet - Adds a lot of health, some damage, and slows when you attack.

Negatron Cloak - Magic Resistance (First part of your Banshee's Veil)

Banshee's Veil - Your big MRes item w/ it's awesome bubble.

Atma's Impaler - Replace your Wriggle's Lantern with this item as your last buy.


-- As always every game is different - Feel free to rearrange these items to fit the situation. I understand that the bulk of my MRes items are late game, but this build was designed to have health to compensate until you can make the Banshee, without sacrificing damage.