Before approaching anybody, most people judge others by their appearance. This is almost an innate feature in the human mind. The reason that this judgment exists is because it is used for reproductive purposes. The more attractive a person is, the more likely they are to reproduce healthy children.
This is something that can be seen through different cultures around the world. One of the more common features found attractive in all cultures is symmetry.
The human brain likes when things are evenly distributed. Because of that even distribution across the face, people who have more symmetrical faces are seen to be more attractive when compared to those with asymmetrical ones.
Attractiveness also is believed to be correlated with the person's health, the more attractive the person the healthier they are. When looking for mates, this will allow women to find men that will provide healthy genes for their offspring, and vice versa. This process goes along with the Good Gene Hypothesis.