I would say that analyzing the theme of silence amongst the townspeople might be a good starting point. One of Miller's main points is the idea that individuals who are silent to injustice actually help to perpetuate greater conflict. As individuals take silence to another level and do not speak out against what is happening, the conflict widens and more people are implicated in the deceit from both Abigail and the ruling order or those in the position of power who are benefiting from the witchhunt. This is evident on a political level. It can also be seen in a personal level for John Proctor's marriage suffers in enduring conflict under the weight of his silence. His relationship with Elizabeth is conflicted through his silence, his lack of voice, his lack of assertion of identity. Through his speaking and articulation, he is able to actually substantiate his marriage, though grave consequences do result.
Fear often leads us to make rash, harmful mistakes. For example, it was fear of getting in trouble for the dancing in the woods that prompted the girls to start accusing people. It was fear of being whipped or hanged that prompted Tituba to "confess" to being a witch and name other women who had joined her. It was fear of the girls turning on her and accusing her of being a witch that led Mary Warren to rescind her testimony against them and accuse John Proctor of being a "devil's man." It was fear of the unknown that led Giles Corey to first talk to Hales about his wife reading "strange books," a confession that would lead her down the road to being arrested. It was fear of Abby's fierce nature and threats that led the girls to keep up their charade of accusations and abuse at the hands of supposed witches. It was fear of criticism and being rejected by his parisioners that prompted Parris to go along with the judges so much, even aiding them in arresting and accusing people. It was fear of the unknown medical reasons that took her babies that led Mrs. Putnam to seek out answers in the underworld, and ultimately accuse Goody Nurse of murder. It was fear of being revealed as a lecher that kept John Proctor from fighting against Abby and the courts for so long. It was fear of ruining her and her husband's reputation that led to Elizabeth Proctor lying about her husband's affair.
As you can see, fear leads people to lie, harm others, and seek answers in unorthodox places. If you focus on how fear is the root of many unfortunate actions, and give the examples I listed above, I think that you'll be well on your way to a good essay! Good luck!