Show you've understood the quote by embedding it - DON'T just say "At one point Macbeth says "We shall proceed no further in this business."" Instead, say "After a long speech exploring his reasons for not wanting to murder Duncan, Macbeth makes his feelings clear when he says to his wife "We shall proceed no further in this business."" Here, the second example shows I've understood where the quote comes in the play and shows I've really understood its meaning.