Spread out when Kennen engages with E + R: his ult only deals damage in a radius around him.

His E + R engage is predictable: when you see him running toward you in ball form, back off immediately.

Kennen is squishy without his burst — if you survive his R, he has nothing left.

Zhonya's is his only survival tool after engaging — burst him before he activates it or wait for it to expire.