I suggest you begin by doing some research on some of the victims of the Salem Witch Trials. There is a lot of literature containing detailed information on specific individuals condemned as witches, complete with excerpts from their "trials".
"Examination of the Records of the Salem Witch Trials" by Margo Burns and Bernard Rosenthal is one such text. You can find part of it at historycooperative.org.
The book "The Salem Witch Trials" by Marilynne K. Roach is a day-by-day account of the events. You can find excerpts from it at books.google.com/books?id=TvxES1lB6XoC&printsec=frontcover.
By reviewing the historical documents about the trials, you can get an idea of what was viewed as "guilty" evidence (having birthmarks, being a holistic healer, a woman in general, or an enemy of those in power) you can get an idea of what not to use. There is a lot of information on this subject out there, so in order to weed out the ostentatious and absurd, make sure you are reading reliable research and sources.
I hope this helps you get started.