Similarity: This includes similarity of people’s beliefs and, to a lesser extent, similarity of personality traits and ways of thinking.
Propinquity: This includes familiarity with the other, which can be caused by spending time together, living near each other, thinking about the other, or anticipating interaction with the other.
Desirable characteristics: This general attraction attribute is particularly focused on an outer physical appearance that is found desirable and, to a lesser extent, on desirable personality traits
Reciprocal liking: When the other person is attracted to you or likes you, that can increase your own liking.