Conformity and individuality are at the heart of this play.

The play speaks to anyone who has lived in a society where the questioning of authority and of the general opinion leads to rejection and punishment.

John Proctor and Giles Corey stand as examples of inviduals who maintain their independence and question the authority of the court in Salem, while much of the town succumbs to the pressure to conform. 

The specific pressures set against Proctor and Giles are directly related to conformity as are the accusations used against them. 

In court, Proctor's choice to avoid baptizing his child in the church is used as evidence against him. This is, on the simplest level, a symptom of Proctor's choice to remain an independent individual. He refuses to conform for the sake of appearances. He has his own opinions and his own reasons for doing or not doing things. In the case of the baptism, Proctor does not want Reverend Parris to touch his children and so chooses to avoid the rite of baptism. 

Proctor's earlier resistance to the town's authority makes him a suspect when he faces the court and accuses it of false deeds. He will not bow to Danforth or to Parris. He stands as an individual set against the will of the group. 

He is dangerous to the proceedings precisely because he does not believe in them.

After his arrest, Proctor is tempted to conform. He is presented with the option of saving his life by betraying his principles and signing a false confession. This confession is, essentially, a means to remove Proctor's individuality and independence and to subordinate him to the power of the group.

Like Giles Corey, Proctor finally refuses to be reduced by the community's impulse toward enforced conformity. Individuality should be honored, in part, because it can be trusted. The group, however, is possessed of a moral bankruptsy, comprised of people who have abdicated moral judgement in favor of conformity. This is a dangerous quality, as the play makes clear. 

Miller demonstrates how peer pressure can lead individuals into taking part in actions which they know are wrong. 

I think that Miller makes clear that the connection between individuality and conformity is one in which both are mutually exclusive in specific settings.  Miller develops Salem as a realm in which conformity is a part of the Salem landscape.  In order to find social sanctuary, one must conform to the condition of false accusations and mendacity in their personal connection to others.  Individuality, as it were, becomes something that is punished.  People like Corey and Rebecca Nurse suffer greatly for their individuality.  Yet, Miller makes it clear that these forces are the heroic elements in a barren environment like Salem.  For Miller, the connection between individuality and conformity is one in which the human being must recognize the intrinsic power of the latter and the potential for destruction that exists in the latter.  In such a construction, Miller is able to make it evident that the individual must be able to recognize the forces of conformity and resist them.  Without doing so, there is a feeling of immense regret, as seen in the form of the Proctors.  In seeing how both husband and wife in their own ways end up validating individuality and rejecting conformity and examining the connection between the two, there becomes a strong message that emerges in the narrative.

How is conformity presented in Arthur Miller's The Crucible?

Conformity is shown to be a fairly brutal element in the drama.  In the introduction to a Penguin Publishing version of Miller's drama, Christopher Bigsby writes about this idea of conformity and the lack of it:

The Crucible is about a time in history where people found the comfort of the community at any costs more beneficial than the discomfort of standing up for what is right.

In this light, the drama presents the fundamental issue of human consciousness as one poised between these incompatible ends of being.  Individuals in the drama must choose if they wish to embrace the comfort of the community, sacrificing one another in the process, or if they wish to stand for something that is more transcendent, and suffer greatly as a result.  The battle between the temporal and contingent identity of conformity and the transcendent, yet painful nobility of independent thought is something that all of the characters have to endure on some level.  It is evident throughout Proctor's own maturation throughout the drama.  His desire to not want to be involved and to retreat is something that faces collision with a growing and menacing threat in which action and confrontation becomes a moral responsibility.  Mary Warren endures this in visceral and physical terms with her testimony in open court, trying to face down Abigail and embodying the very essence of "discomfort."  Her "crucible" in this instance ends with her running back to the community in the form of Abigail's arms and condemning Proctor.  In the end, how characters respond to the polarity of conformity with a known wrong and a lack of conformity in standing up for what is honorable and decent in a world that lacks such values becomes the essence of both Miller's play and the time period that envelops both it and the reader.