If you play Kennen, you have to know his item build. Kennen really don´t need much ap to get much kills, but if you want a good game you have to get your Boots and you Vampiric Scepter as fast as you can.
When you got about 60-70ap you go to any lanes and gank them.
You skill combo is Q-E-W-Q
If you already got your ulti your combo is Q-E-R-W-Q
The most enemys are almost dead after that.

If you go to play Kennen, every time try to get mid lane.
Then, the first 4 level you are lasthitting as much as you can. (If you don´t you won´t be good lategame)
When you´ve reached level 4 you try to get your enemy.
Just harras him with you Q until he has got half life and then finish him.