A story, whether novel or screenplay, has two tracks that influence and guide each other:
The Story Question is the question asked by the External Story:
Will Van Helsing be able to destroy Dracula? (Dracula)
Will Tyler be able to find and bring back the Nazi Enigma encoder? (U571)
Will Indiana be able to find the Holy Grail? (Indiana Jones and the Last Crusade)
Will Toula be able to get happily married? (My Big Fat Greek Wedding)
Will Phil be able to break out of February 2nd? (Groundhog Day)
Will Frodo be able to destroy the Ring? (Lord of the Rings I, II, and III)
Will Luke be able to destroy the Evil Empire? (Star Wars IV, V, and VI)
Will Harry be able to destroy Voldemort? (Harry Potter series)
Will Rocky be able to *go the distance* fighting Apollo Creed? (Rocky)
Will Forrest Gump be able to convince Jenny to stay with him? (Forrest Gump)
I'm blanking on more films/novels, but you get the idea.
If a story is going to be engaging, it must have a clear-cut story question. This is the goal that the protagonist is motivated to pursue -- it is a tangible goal and something that will be answered at the end of the story with a clear Yes or No. There are sub-goals in the story, of course: for example, Frodo must get through the Dead Marshes, but these sub-goals are steps to complete the main goal.
The story goal doesn't have to be established right up front, but if not there should be another goal that's very important to the protagonist, and the story goal needs to be put in place pretty quickly. For example, in the Wizard of Oz Dorothy starts with a bridging goal: in Kansas Miss Gulch has taken Toto, and Dorothy is determined to get Toto back. She succeeds but then is quickly lifted up by the tornado into Oz where she immediately develops her Story Question: will she be able to get home?
The Story Goal should be something that your hero wants desperately, and will give maximum effort to achieve. Instead of just being blown around, he will act and cause events to occur in order to achieve this goal. He will struggle: the goal should be something very difficult that takes a great deal of courage to achieve. The story goal should have a number of obstacles, including a *chief obstacle* of some sort, often an antagonist, but it can also be a situation.
You need to make your protagonist sympathetic so the reader or viewer will care deeply about whether your hero actually achieves his goal. I'll talk about facilitating reader-identification tomorrow.
6 hours ago