The actor playing John Proctor would have to look like he is in his mid-thirties. He is described in the liner notes as "powerful of body, even tempered and not easily led." He would have to be well built with a general facial expression of confidence. But since he is one of the most dynamic characters and goes through many emotions, the actor would have to be versatile. This is why Daniel Day-Lewis played the role so well in a film version.
Abigail Williams is seventeen, "a strikingly beautiful girl, an orphan, with an endless capacity for dissembling." To dissemble means to conceal one's true emotions. So, you would need a beautiful actress who is a very good actress because Abigail (the character) acts in the play itself, lying and pretending to be assaulted by spirits.
Reverend Hale is "nearing forty, a tight-skinned, eagle-eyed intellectual." He takes pride in his work so that pride should be shown in his facial gestures and general demeanor. However, he is not closed-minded. So, he should also act with general curiosity. An actor who is able to give off a proud but open-minded attitude would be a smart choice.
Mary Warren is seventeen, timid, and naive. The actress would have to look the same age as Abby, but not quite as attractive and certainly not as confident or scheming.
Deputy Governor Danforth is a "grave man in his sixties." He is uncompromising. So, the choice would have to be an older actor capable of acting like someone determined and set in his ways. Danforth is stubborn; he will not have the court's reputation tarnished even if the accusations are untrue.
Reverend Parris is in his mid forties. "In history he cut a villainous path, and there is very little good to be said for him." A stern middle-aged man, probably of normal build, Parris is more worried about his reputation that the spiritual state of Salem. As he is always anxious and worried about himself, the actor would need to appear defensive, "villainous," and determined.
Giles Corey is an old man, muscular and still powerful. His is like an old man set in his ways but he is innocent and brave. The actor should be an older man, powerful and with a general look of goodness.