The first thing guys notice about a woman is typically her face, particularly her eyes and smile. This is because the face is the most expressive part of the body, and it can convey a lot of information about a person's personality, mood, and intentions. A warm, inviting smile can be very attractive, as it suggests that the woman is friendly and approachable.
Guys might also notice other physical features, such as a woman's hips, waist, and legs, but the face is usually the first thing that catches their attention. This initial assessment is based on instinct and cultural norms, as facial features are often associated with attractiveness and desirability.