At the outset of any good story, we find our protagonist, and see him/her in their normal surroundings. An event occurs, and Hero is thrown out of his comfort zone and into the Situation, which is the core idea of your plot. This is the circumstance in which your protagonist finds himself in the beginning of the story.
In the opening pages of The Hobbit, by J.R.R. Tolkien, a respectable hobbit, Bilbo Baggins, is living a comfortable life in a prosperous, sheltered village, and has no desire to change that in any way. However, a casual, polite greeting made to a passing wizard sets a string of events into motion that will eventually change the course of history of Middle Earth.
The wizard, Gandalf, tricks Bilbo into hosting a party for Thorin Oakenshield and his band of dwarves, who sing of reclaiming the Lonely Mountain and its vast treasure from the dragon Smaug. When the music ends, Gandalf unveils a map showing a secret door into the Mountain and proposes that the dumbfounded Bilbo serve as the expedition’s “burglar”. The dwarves ridicule the idea, but Bilbo becomes a little indignant, and joins despite himself. The next morning he has second thoughts, but the last minute Bilbo literally runs out the door, with nothing but the clothes on his back.
- How will the story start?
- What is the hero’s personal condition (strength, health) at the beginning?
- How will that condition be changed, for better or worse, by the hero himself or by the antagonistic force?
- What could possibly entice him out of his comfort zone?
Now we come to the next part of the core of your plot: Objective
A protagonist has no business showing up on the page unless he/she has a compelling objective. If he doesn’t want something badly enough to do just about anything to achieve it over the next couple hundred pages, then he doesn’t deserve to have a story told about him.
Bilbo does have an objective. Once he gets past his feeling of having made a terrible mistake, he desires nothing more than to help his friends achieve their goal: that of regaining their lost kingdom. Gandalf exerts a parental influence over Bilbo at the outset, guiding him and pushing him out of his comfortable existence. But it is Bilbo who has common sense and compassion, who gradually takes over leadership of the party, guiding and rescuing them from their own greedy mistakes. This is a fact the dwarves can’t bear to acknowledge, and also a fact he doesn’t realize himself.
Those turning points where with each adventure Bilbo gains confidence and a tool or weapon he will later need are what make up the best parts of the adventure. That is what you must inject into your adventure, be it urban fantasy or science fiction.
- At the beginning of the story, what could the hero possibly want to cause him to risk everything to acquire it?
- How badly does he want it and why?
- What moral (or immoral) choice is he going to have to make in his attempt to gain that objective?
Perhaps your tale is set on a space station. What does your protagonist need that is in short supply? What does he have to do to get it?
Perhaps you are writing an urban fantasy. Perhaps your main character is a vampire. He/she requires sustenance–what will he/she do to get it? Or conversely, if a human, what will he/she do to avoid becoming vampire-food?
Protagonists begin their tale in their current surroundings. They are thrown out of their comfortable existence by circumstances, and forced to identify objectives they must achieve or acquire in order to resolve their situation.
Circumstances and Objectives combine to form the plot. Character A desires Objective B–and will do anything to acquire it. Along the way, Character A has a series of adventures that force him to grow and change, but which in the end give him the strength, the moral courage to enable the final resolution.
Thus, whichever you conceive first, characters or objective, you need to know why your character is willing to leave his circumstances and embark on his adventure. That objective must be compelling enough for him to risk everything he values to achieve it.
But what if a side character has such a compelling story that the book becomes about him, and not our hobbit? If you notice that is the case, rewrite your book so that the character with the most compelling story is the protagonist from page one.
Potential for gain must outweigh the potential for loss–so if he is risking his life, there had better be a damned big payoff at the end, whether monetary or in moral coin. Without that risk and potential for gain, there is no story.