The sign that Betty Parris was bewitched is right at the beginning of the play. She is lying on her bed and won't respond to anyone. It seems like she's in a coma or something and will never wake up. She has been like this ever since her father saw her in the woods.
Cheever goes to see the Proctors because he has a warrant to arrest Elizabeth Proctor. He is also supposed to search the house for poppets (dolls). This is because Elizabeth has allegedly bewitched Abigail Williams by using a poppet. Cheever ends up taking Elizabeth away.