Introduction Kennen's abilities.

Mark of the Storm: Each of his abilities apply a mark on the target. When the target reaches three marks, it will be stunned.

Basically, it is what makes Kennen ... KENNEN. Without this passive he is a lot less powerful because he's force is he's stun.

Thundering Shuriken : throw a fast moving shrunken in a line . deal magic damage and apply a mark .

this is kennen most useful skill . it have low cd and hight damage so just learn to aim ( it is a skillshot ) and kill people

Electrical Surge : passively each few attack , your next attack will deal bonus damage and apply a mark .
when you use it , each enemy around you who have a mark of the storm will receive magic damage and receive an other mark of the storm .
i like to max this skill second because the passif is good to harass and to put a mark on the enemy and the active shine in team fight

Lightning Rush : you transform into a lighting ball gaining armor and magic resist and dealing damage + adding a mark to each enemy you pass through .

this skill is a good tool to escape/chase or to add a mark to enemy but i won't max it until last because i only use it to put a mark of the storm and to move faster .

finaly Slicing Maelstrom : you create a maelstrom around you and each 0,x second you deal magic damage to a target ( max 3 time each target ) and you apply a mark .
one of my favorite team fight ultimate because after 2 second almost all the enemy will be stun . that skill can let you 1vs 2 or 1 vs 3 if you have a good stuff .