Obviously her face, and more specifically her eyes. That's the first thing humans focus on when looking at other humans.

I'll give you a clue... O_O ... I guess this question doesn't have to be answered in romantic terms (if it is, sorry, my mistake ! feel free to tell me to get the hell out of here ^^ but be kind ... ) When I meet someone (whoever, guy or girl) I always always always always 'notice' the eyes... not only the eyes, but the way this person looks at me. =)

Her eyes! It's the only thing we can not change or fake somehow. We can change our body or some of its parts, our hair-cut, make-up etc. We can even smile when we feel sad or look sad when we are happy inside, but our eyes will say all the truth about us. In Russian there is even such a proverb: "Глаза - зеркало души." ("The eyes are the mirror of the soul.")

This is eventually a question for men. Anyway, I am going to answer it, because I want it: :D Q: When a man look at a woman, what is the first thing he notices? A: What she wants he notices first. :)

If you are a man you should know the answer to that one already.