Ruby pier is a good symbol because you can learn alot about Eddie here. The pier is where he grew up and eventually started working there, Eddie later even died at the pier attempting to save a young child.
The Diner was a very important symbol because it helped Ruby explain why she was one of the people that Eddie met in heaven. It however then evolved into a way to teach Eddie to forgive his father.
The Weddings represent what Marguerite's heaven was consisted of. At the beginning of the chapter he is remembering the time that he had with her and is sad, but when he learns why she loves weddings so much he is happy that they are at the place they were married.