The most commonly used structure for fiction stories is the so-called Three Act Structure or Traditional Structure, which is divided into Introduction, Knot and Ending.
There are usually a few critical points at the end of the introduction (called a trigger) and at the end of the knot (turning point) to propel the stories forward. The basic outline for fantasy novels and stories for role-playing games is:
1.1 Presentation: The presentation gives us the sense of the story. It gives us all the necessary information to get the story rolling. Generally we are made to know with details, descriptions or situations the Statu Quo (the state of things at that moment) as well as the definition of the genre (horror, comedy, etc.) and the rhythm.
The beginning of the movie The Lord of the Rings: The Fellowship of the Ring, where the fantasy world and the normality of it is introduced.
1.2 Tone: To establish the tone or mood of the narrative, special attention must be paid to the setting, location, and character details. Our way of placing the characters and describing where the story takes place will set the tone we plan to maintain.
The beginning of the story of "The Lord of the Rings" has a cheerful tone to introduce the "normalcy/Status Quo" of the hobbits. But this tone is frequented by serious, cold, horror-laden dialogue and scenes that foreshadow the evil and hardship that will be encountered in the rest of the adventure.
1.3 Trigger: This is a dynamic event that draws the reader or players into the story. The main objective or problem may not appear at the moment, but something happens and this generates interest. It may be an action (someone is killed), a dialogue (a character receives a mis-terious phone call) or a particular situation (a character is thrown into a circumstance that he or she may not be able to handle). The trigger at this point can be a McGuffin.
In The Lord of the Rings: The Fellowship of the Ring, the trigger is the moment when Bilbo gives the ring to Frodo..
1.4 Conflict: Something that is important to the protagonist or the players is revealed to us, something that he must do, that he wants to achieve or that he is obliged to carry out. There's no need to feel bad about putting our protagonist through an ordeal, that's what it's all about.
Continuing with The Lord of the Rings: The Fellowship of the Ring, the conflict is when they discover what the ring is and that its owner wishes to retrieve it to conquer Middle-earth.
1.5 Villain: The presentation of who or what opposes our protagonist may not be so clear and evident, but something of his character, his activities or his purposes must be glimpsed in the approach. If nothing more than a sense that something bad, unknown, is coming.
In the case of The Lord of the Rings, at the beginning there is an introduction of Sauron and later, before entering the knot, Frodo has an encounter with an extension of it, the Nazghuls.
1.6 Protagonists: All the main characters of the plot should be introduced as soon as possible, and it would be good to show the secondary characters as well. Remember to keep the list of main characters to a minimum, it is very difficult to follow more than four main characters at the same time.
In "The Lord of the Rings", all the main protagonists are introduced during the beginning up to the moment of the Council of Rivendell, from this moment on, the rest of the characters are secondary.
1.7 Narrative twist: It is a moment when something happens or a determination is made, after which the story takes a new direction and makes us intrigued about what will happen next. It usually marks the end of the plot, when the protagonist decides to act, reacting to the trigger.
The Council of Rivendell decides to create a company to destroy the ring. This company will be led by Gandalf the Grey.