Alien: A Novel Download What Characteristics Would An Alien That Resembles A Human Have?

What characteristics would an alien that resembles a human have? - alien: a novel download

I write about a stranger who looks human, but it is not. How can I always think a stranger in the human world? What characteristics should such cries of the Alien? This is not a novel or something I'm not trying to ideas to steal, why I do what is realistic. Should any special ability that it does not appear to humans? I really need some advice. Thank you!