Finding the heart of the play
Try a trick. Gather together the pages of the text of your chosen play – not including any introduction or prefatory material – and try, as accurately as you can, to open the play in the middle. Look at where you are. Who is on stage? What is going on? What is the effect of the scene to the development of the plot? It doesn't always work, but often the chronological mid-point in a play gives us something central: an event, a tableau, an encounter, which we might construct as in some way pivotal.
Here are some examples. In Romeo and Juliet, for example, the centre-point of the play is the death of Mercutio, brawling with Tybalt. We might see this first death in the tragedy as a signal that things cannot now go well; the death of this jesting character who dies on a joke – ‘ask for me tomorrow, and you shall find me a grave man’ (3.1.89–90) – marks the end of the lightness with which the Montague/Capulet feud has been temporarily leavened. Chapter 6 considers Shakespeare's use of his sources in more detail, but it is interesting to note here that Mercutio is one of Shakespeare's most substantial additions to his sources: what would the play be like without him, and why, having invented him, does Shakespeare have to kill him off at this point?