When Hanna stands up to turn the TV off, she throws her napkin/towel on the small table in front of her. It covers most of the table, and also part of her plate (on the right side of the table). When she has turned the TV off and looks back at James, we see the towel lying neatly on the left side of the table.
When Clayton and Betty are by the car talking with the open car door between them, from one angle Betty is seen with her left hand on her hip then shown from the reverse angle her hand is on top of the car door.
Before starting his line about James Whale wanting "to draw him like a statue" Clayton tosses away his towel. James turns from the window and Clayton punctuates the end of his line by tossing his towel away again.
When Clay is in the diner and is about to watch "Bride of Frankenstein" on TV, Harry, the man at the end of the bar, is reading a paperback book but in the next shot, he is reading a pamphlet. And when Clay says, "We're watching the damn movie, Harry," Harry is holding a book again.
The goof item below may give away important plot points.
Clayton attempts mouth-to-mouth resuscitation and chest compressions on James Whale. This CPR technique was not widely used until the 1970s after heavy promotion by the Red Cross to get the public to accept the procedure. The common practice during the 1950s involved raising and lowering the victim's arms.