See, most people build Kennen AP, also known as "the stupid way". Here are the reason he shouldn't be built AP.
1. All his ratios are terrible.
2. Strait AP he is way to squishy and dies all the time.
3. People who build him AP are just bad in general.

Ok now that is out of the way, Kennen (in this build) is a DPS, slight off tank. He excels at side laneing and if absolutly necessary it is POSSIBLE to mid. Never take mid unless you are the only ranged champion on your team.

The only thing you must alway keep in your mind "FOR THE LOVE OF GAWD NEVER OVER EXTEND", for if you do BOOM you are dead, not big surprise.

In marks take flat Magic pen.
"But i thought you said AP Kennen was awful" Yes i did say that little ***ola still he is mainly spell damage so it helps.

In seals take flat Armor.
This will give you more survivability early game, where you need it most.

In Glyphs take flat AP.
Before you say it lil ***ola a little bit of AP early game from masteries and runes helps get you fed.

For Quints take the all popular flat Health.
Reason- see seals

You need as much damage output as you can possibly get so take Attack Speed, AP, Spell Penn, and Armor Penn.

In the defensive tree you take Armor, Dodge, and Move speed after dodge. That will help you live and escape.

Thundering Shuriken- A basic skill shot that adds a mark of the storm. Your bread and butter. Its 45 energy and a decent amount of damage. SPAM ALWAYS. Should be first skill to max and first skill you take.

Electrical Surge- Passive: every fourth attack you deal bonus damage. Active: strikes any target
in the vicinity with a bolt of lightning. Very helpful skill, should be leveled up 2nd and taken first at level 2.

Lightning Rush- You run really fast, deal some damage and add a mark of the storm. This is the reason you don't need ghost. It is a very helpful skill when combined with Electrical Surge for farming. It is a GREAT skill just not as great as the others, take at level 3 and level it up last.

Slicing Maelstrom- The GOD of giant AoE stun. Helpful around one, or five enemies. Deals good damage with a stun most of the time. If used correctly it can turn around a Team fight or in 1v1 will basically GARENtee a kill. This ult is a scary sight to behold, players run in fear when that hear it, don't be afraid to use it just to scare people away from pushing turrets. Just don't ONLY use it for that, and use your better judgement if they have almost killed the turret not worth trying to scare them off with it. So just don't be stupid with it and you can make AND break teams with it.

Good
exhaust-will help you get kills and escape
ignite-great for the champions who just barley escape, slap that on and BOOM got your self a kill. Also helps destroy a Warwick because of the healing reduction

Decent
flash-i can see why you would take it, but its not my type of spell
teleport-helps you get around the map useful, but not as much as exhaust or ignite
cleanse-helpful because kennen can get shut down with cc

Bad- now with reasons!
ghost- you have lightning rush for this, wasting a spell
rally-... do i have to explain?
fortify- not for you, have a tank take it.
heal- you should be killing them to fast for them to hurt you... too bad
smite- you are NOT a jungler
clairvoyance- one again, not for you

WTF ARE YOU THINKING YOU BOOT!
clarity- you don't ****ING use mana.

Only if your pro
Revive- This is only good is you can live for the 9 min cooldown, if you can u never leave the lane and you NEVER DIE.

with Kennen there are certain champs you mid against, and some you stay FAR away from.

Good Champs to mid against:
Ezreal
Veigar
LeBlanc
Swain
Ashe

You can tear those champs apart in the laning phase

Champs to stay FAR away from
Vlad
Akali
Anivia (****ing egg)
Caitlyn
Twisted Fate
Tristana
Heimerdinger

The champs listed will bend you over their knee and then ***-RAPE you so hard you won't walk for weeks. stay FAR AWAY FROM THEM.

Pros

Great farmer
Can harass like a boss
Has a VERY good spam skill
Has a reliable stun

Cons

Squishy until Force of nature is bought
Can get shut down by disables
Gets Focused 99.99% of the time
Not the best tower pusher

All tanks and the over all best person to lane with ever is...

AP SION


Don't Lane With
any physical or ranged carry, they will take all your kills and you need the MUCH more than them.