MetaphorsThe reoccurring cigarette metaphor is a good example of storytelling because it shows how Augustus's opinion of himself progresses throughout the story. At first, he sees the cigarettes as something he has power over; this stems from his inherent desire to control his own destiny and to make something of himself. Later, when he tries and fails to buy the pack of cigarettes at the gas station and Hazel has to save him from his infected g-tube, it shows that Augustus no longer has power over the cigarettes because he can't even buy a pack without someone's help. It is symbolic of him deteriorating, weakening, and losing his grip on life. In his last days, Augustus hates his body for limiting his character which is contrary to the control and confidence he felt in the beginning. Nonetheless, he still fulfills his inner desire to leave a legacy by writing the sequel of An Imperial Affliction to Hazel. Though he doesn't end his life as the hero he imagined himself to be, he becomes a hero to Hazel and an inspiration as a person who loved with all his heart till the end.
In addition, Hazel compares herself to a grenade because she believes that she will leave a deep emotional scar on her loved ones once she inevitably passes away. The metaphor of a grenade is a good example of storytelling because it highlights how death is so sudden (like the explosion of a grenade), how death affects everyone that is close to the person (like the people close to a grenade), and how death leaves emotional scars that take an extended period of time to heal (like a grenade leaves gashes and deeply penetrating wounds). However, because Hazel had a near fatal visit to the hospital but survived, she is able to see what is it like the be the grenade. At the same time, Gus is the first of the two to pass away, so Hazel also gets to feel like the person hit by the grenade. This is a fantastic example of storytelling since the reader is able to see both sides of the situation through the very intimate and personal perspective of Hazel.
John Green makes extended use of foreshadowing which build suspense and keeps the reader guessing. This makes for an engaging story and builds emotional attachment. For instance, although this isn't mentioned in the movie, as Hazel and her mom come to pick up Augustus for their trip to Amsterdam, they overhear Gus yell, "BECAUSE IT IS MY LIFE, MOM. IT BELONGS TO ME." This outburst foreshadows that something isn't quite alright with Gus which turns out to be his cancer recurrence.
In addition, during the actual flight to Amsterdam, Gus and Hazel make a conscientious effort to synchronize the playback of their movie, but Gus's movie starts a couple of seconds earlier which is both symbolic and foreshadowing of the fact that Gus will pass away sooner than Hazel.
These are just some of the examples of good storytelling techniques. I have personally reread the book three times, and each time, I notice more and more minute references and links between seemingly random additions to the story. That's what makes a good story a good story: it gets better each time you tell it.