John Proctor is the hero of the tale, but he is not without his flaws. He is opinionated, blunt, hard-working, conflicted, and brave.
In Act One, we see many of these traits surface. He states his opinions quite frankly and bluntly, not caring who he offends; he would rather state what he feels are important truths than keep quiet for fear of offense. He lets Reverend Parris know right off what he thinks of his choice of topics for sermons. John states, in front of Rebecca Nurse, Giles, many of the girls and the Putnams that he feels Parris preaching "only hellfire and bloody damnation" have driven many people away from coming to church. He defends his opinions in this same act, saying vehemently, "I may speak my heart, I think," which describes Proctor in so many ways. He does speak his heart--he doesn't hide it. When Hale questions him and his wife, he confesses he hasn't had his child baptized because
"I like it not that Mr. Parris should lay his hand upon my baby."
So, Proctor is an opinionated man who speaks bluntly and openly for all to hear.
Proctor is also a hard-working farmer. In the beginning of Act Two he mentions that he was out all day planting seeds. Later he mentions how hard he works, from dusk to dawn, which makes it hard to get to town very often. He also works very hard at freeing his wife and friends, even at his own personal risk.
Bravery is something else that Proctor shows; after seeing Giles Corey and hundreds of others arrested for questioning the courts, he still tries to go against them. He even openly admits his affair with Abby, telling them, "I have known her," in order to try to discredit Abby's reputation. He bolsters Mary Warren as she tries (and fails) to be brave, and in the end of the play, he refuses to confess, instead being hanged for his honesty. He bravely faces his own death, knowing that his sons can "walk like men in the world" because he maintained his integrity.
I hope that those thoughts help to get you started; good luck!