People form relationships by being either attracted by or to others based on five major factors shown below:
Similarity
Most people are more likely to follow the similarity principle, according to which they tend to be favor of those who share the similar status or personalities except for the others who instead follow another pattern called complementarity, where they act in an exactly different ways.
Proximity
Among interpersonal interactions physical closeness plays an important role by increasing the opportunity for people to meet with one another, which as well sets the stage for further relationship.
Reinforcement
People are more attracted to others who offer more rewards in different degree. More interestingly, people who have received favors from others are also more attractive due to an obstinate belief that ones who worth such favors are as well worth to be trusted.
Physical attractiveness and personality
Compared with physically unattractive people the attractive are more welcomed, who unobviously radiate a sense of familiarity to others. This is also true with people with pleasant personality.
Socioeconomic and educational status
Higher socioeconomic status draw more attention to women but receive less concern from men. In fact, men care more about physical attributes instead of higher socioeconomic status in building relationships with women