In the opening of the play, how does Priestley hint at events which are to come in the rest of the play?

In the play's opening, there are various hints of things to come. First, Mrs. Birling corrects her husband about complimenting the cook... who shouldn't even have been addressed because of the difference in class, enhancing the fact that she doesn't see the cook as a person.... merely hired help. Second, Sheila takes Gerald to task for his behavior the summer before, alluding to the fact there was a reason for his staying away.... what could it have been? Third, Sheila is more excited by the ring she recevies, than the man she has become engaged to marry.