Many social movements are created around some charismatic leader, i.e. one possessing charismatic authority. After the social movement is created, there are two likely phases of recruitment. The first phase will gather the people deeply interested in the primary goal and ideal of the movement. The second phase will usually come after the given movement has had some successes and is trendy. People who join in this second phase will likely be the first to leave when the movement suffers any setbacks and failures.
People who join social movements usually consist of individuals who are deeply committed to a set of goals and support the goals of the movement. Others who join are perhaps insecure and may enjoy being a part of the movement. Curiosity about a movement's activities and the use of these activities for their personal interest might be cause for yet other individuals to join. While the preceding types of people join social movements, I would like to point out reasons behind their decision to join. Activists maintain relationships with like minded people which allows for recruitment through networks. Movements thrive from the development and maintenance of a strong social network. People are attracted on how the movement frames perceptions. Movement appeals to those who feel disenfranchised and provides a sense of empowerment or understanding of for disillusionment. Individual participation may also derive from a disjuncture between legitimate expectations and perceived expectations of the movement.
Social movements are more likely to evolve in the time and place which is friendly to the movement.