I'll be referring to
[this diagram] of the three-act structure, and I'm going to use The Lion King as the example (mostly because mapping it to this was an assignment in my high school's base-level senior English class, which I find very funny).
Act One: Set up. We learn who the characters are, what the world is, and what their internal and external motivations are
Beginning: The whole circle of life song/scene. We see that the animals all serve and adore their king, we learn a prince is born, and that there's themes such as the cycle of nature and the divine right of kings
Inciting incident: Mufasa asks Scar why he didn't attend the ceremony. We learn what Scar wants (to be king) and why (because he feels inferior to his brother) so when Scar does the things he does later, we know why
Second thoughts: Simba, our protagonist, learns about the elephant graveyard. His dad told him one thing (don't go there) but his desire to do what he wants his own way (as were told in I can't wait to be king) makes him choose to ignore his dad's judgement and go. Scar tells him this info to get the chance to kill Simba, because Simba is an obstacle as to what he wants
Climax of act one: Simba and Nala being chased by the hyenas and Mufasa having to save them. It's an action scene, which those little explosions on the chart tend to be, but it tells us how Simba will be brave when needed. Mufasa could have killed the hyenas but let them go, which tells us about how he is a just king.
Act Two: Confrontation. This is when stuff starts to escalate. Characters are going on the course of their adventures/journeys to accomplish the things they want to do (or need to do). They do these things because of events in act 1 and they do things that follow their character
Obstacles/ascending actions: Scar puts his plan together to kill both Mufasa and Simba and become king. His prior plan failed so he has to do something more drastic, because he's not going to stop at the first failure. He lies to the hyenas to get them on his side, because he knows that he's too physically weak to do this on his own. He thinks he's smarter than they are so he has no qualms about using them like this. He also tells them they can kill and eat as much as they want, which is disrespectful to the circle of life. We're told and shown how he is not fit to be a king because of his beliefs
Midpoint: The wildebeast/Mufasa's death scene. There are multiple things that happen immediately leading up to this (Scar lying to Zazu to get Mufasa to come, Scar tricking Simba to get him in the canyon). The midpoint/twist and height of drama is when Scar digs his claws into Mufasa and kills him. Mufasa is a good person and always believed in the good of his brother, so this betrayal hurts, a LOT, and you can see that in his face.
More obstacles: Simba has to run away because he believes people will blame him for Mufasa's death. He almost dies in the desert, and there's lesser obstacles like learning how to be an insectivore and throwing away his old life to live with Timon and Pumbaa. He wants to make his dad proud and be king but he believes he can't do that because of the lies Scar told him. His goal (to be king and do what he wants) is thrown away
Disaster: The Pride Lands fall into ruin. This doesn't happen for no reason, it's because Scar is a bad king. We're told that the hyena overhunt, which is something he told them they could do in Be Prepared. The world is suffering because Simba isn't doing what he needs to do (the whole divine right of kings thing). Nala leaves to get help (which, in hindsight, I'm not sure what she's expecting to find, besides Simba, because she read the script and knows she needs to do this).
Crisis: Simba, well, has a crisis. Nala tells him what he NEEDS to do (be king) and he tells her what he WANTS to do (live in peace and not face his "crimes"). He knows it's what he SHOULD do but he doesn't believe he'll be able. The clash of wants vs needs (internal vs external motivation) gives characters challenges to overcome, and that's more interesting than trading in plot coupons.
Climax of act 2: Mufasa appears in the sky and tells Simba what he needs to do. It's something he NEEDS to hear. He's told he's the rightful king and bring balance to the Force. He makes the decision to confront Scar (and confront his demons) which sets us up for act 3.
Act 3: Resolution. We have exact goals and we know exactly how to accomplish them. Characters are going to do these things because of their character, and there have been clear steps building up to this.
Descending action: This is the "Oh yeah, it's all coming together" meme manifested. Scar is king because of his actions (killing Mufasa/Simba), which he did because of his already established wants/needs (he doesn't want to feel weak/inferior). As the villain, his actions have set up his downfall (the hyenas overhunt, which drives Nala to find Simba, and they do so because he told them they could, because he will lie to gain power and he doesn't care about the circle of life). The hero confronts the villain because of the prior incidents. He doesn't do it because he's good and the villain is evil, he does it because he wants/needs to.
Wrap-up/End: what it says on the tin. Simba doesn't kill Scar, because he, too, is a just king, but Scar is killed by the hyenas because he lied to them. Simba taking the throne causes rain which makes the priedlands green again, which is the whole divine right of kings thing again. The other lions learn the truth about what happened to Mufasa and we all live happily ever after
Things in stories should do multiple things at once. The circle of life opening tells us the themes of the movies, it tells us the setting, it tells us the characters, and all without any dialogue or narrator. We see pretty things, we get a feel for this world and how it works etc. Some of the scenes that were cut out were the morning report song, which is a fun little song and tells us how different animals work with each other, but the important stuff (Mufasa teaching Simba how to pounce) can be accomplished without it. There's also a scene of Scar hitting on Nala, because what's a king without a queen, and what's a king without heirs? With heirs, Scar can rule forever, long after he dies. But we already know he's single-minded in his goal (to be king, at all costs) and that he's willing to do gross/immoral things to do so. That's not in the movie, but it's in the Broadway show because it's longer. There's another version where he does this with Sarabi (Mufasa's mate/Simba's mom) instead, which is also gross/immoral, but it's a little more obvious that he wants to completely replace Mufasa. But again, this is stuff we already know. We don't need a scene of him hitting on his sister-in-law to tell us he's a bad guy, him killing Mufasa and trying twice to kill Simba is enough.
So when you're plotting, ask yourself, WHY is this character doing this? WHAT is their motivation and their thoughts behind it? Ned Stark wasn't killed because the script said he had to be killed to piss off the various Stark children and start a war. He was killed because he believed the Lannisters would "do the right thing" and follow social/political norms. He struggles between his duty to the king and his duty to his family (and the people of the north). That struggle and that misplaced trust caused him to die. But the Lannisters didn't do this because the script told them to be bad. Twyinn sings the Rains of Castamere, which is about one branch of the family brutally murdering the other. Jamie betrayed his king and killed him (this is framed as a "good thing" since the last king was a Bad Guy, but he still broke the rules of society/politics to do this). He also tries to kill Bran in the first episode.
The reason why game of thrones was "good" was because characters did things because it's something they would do in their situation, based on what we know of their morals and character. The later seasons turned bad because characters did things because that thing had to happen for the next thing to take place. The night king had to die so that we could go to king's landing. Dany turned into dragon Hitler because she has to be bad enough for Jon to kill her. She killed those civilians because she needed to become dragon Hitler. And she killed them because her other dragon died, as did her best friend. The dragon died because she "forgot" about the Greyjoy navy. And she forgot because....well d&d needed a reason for it to happen. Compare this to earlier in the series, where she puts the dragons in baby jail because they killed an innocent girl. It hurts her to do this, but she does it because she doesn't want people to be hurt like that. The dragons are her children, but she sees herself as a kind and just ruler, a protector of the weak, so she will do something that hurts her own children in order to protect her people.