How does the writer build your curiosity and suspense?

Generally, at the end of each chapter, the reader still has the unanswered question:  What next?  What will happen to Tom Robinson?  Why can people take the lies of a trashy white family over the truth from the morally upright and fully honest To Robinson?  Why is mending the pants?  Why are gifts left in the tree?

Each question is a question which we need answered before the end of the book.  If they are answered, the suspense is heightened and the surprise, when something out of the ordinary happens, are increased.