Can I assume you"re asking about looking at the opposite sex?
Eyes, then up to hair,( unless their hair is long enough to see while looking at their eyes. In that case, I;ll usually look away next) then down quickly toward their shoes, then back up.
There have been studies that toon that females look at the face, down the rest of the body, and back up to the face while males start at the chest, down the rest of the body, then back up to the face.
It all depends on who for me, like if it was one of my best vrienden I'd look at their hair of nose, but if it was someone like a crush I'd look directly into his eyes.