Having written several short stories and novels, I imagine I have a good idea of what comprises a story. Many others think the same thing, regardless of their level of writing proficiency. All you need to a story is a beginning, middle, and an end, right?
Perhaps on the basic level, yes. In practice, though, not every story that has a beginning, middle, and end will be worth reading.
So, what else is there?
In a nutshell, a story is all about the characters, their goals, and the obstacles they have to overcome to get there. As an example, I'll use my second novel, Friends in Deed (and for those who don't want spoilers, close your eyes until we reach the end of this post)..
This story is about a character (Aston West).
Now, to work on Aston's goals requires us to dive into some additional details. More so with novels than with short stories (which in general are going to be too short to add too many goals into), your character is going to need a major goal spanning the entire book. But in the meantime, Aston is also going to need some smaller goals that pop up throughout the book. Without these intermediate goals, the reader is going to get bored and when that happens, they tend to set books down and not pick them back up (better known as the author's death knell).
Aston's major goal here is to escape from the Cassus twins. This goal starts off very early in the book, spans the entire story and once it happens, it's time for The End.
As far as minor goals, there are several that pop up throughout the book. Some are larger than others, and some are quickly solved. Some are goals that he sets for himself, and others are ones imposed upon him by others. For example, Elijah Cassus (one of the main antagonists) forces Aston to help mount a rescue from the prison planet they once both inhabited. This goal takes place during the first portion of the book (I won't bother going into what the goal is for the second part of the book, to avoid spoiling it all for you). As another example of a slightly smaller goal, a native of the planet captures them all and he needs to convince their (mentally ill) captor into releasing them.
Within these minor goals, you can somewhat see where we're going in terms of setting up obstacles that your character needs to overcome.
Aston needs to escape from the Cassus twins (major goal), but Elijah forces him to help mount a rescue by threatening to turn him in for a mandatory death penalty for past crimes. He can't easily mount an escape without overcoming this threat, so he's going to have to figure out a way to negate this threat.
Aston has to mount a rescue from the prison planet (minor goal). Many obstacles began throwing themselves in his path to prevent him achieving this goal. First off, he and the team leader are at odds with each other (conflict). Then, they discover that the team member they want to rescue has been captured by some of the planet's inhabitants. After they overcome this obstacle, the team's ship is destroyed by the planet's overseers and they end up captured by the mentally ill inmate (setting up another minor goal to achieve). Once they achieve this goal, they have to find a way to make it off the planet (another obstacle to achieving the original minor goal of having a successful rescue).
So, as you can see, goals and their obstacles can (and should often) overlap each other. This is part of what makes an interesting story that people want to read. So, to recap, take one of your stories/novels and ask yourself the following questions:
Who is my main character?
What do they want to achieve? What is their major goal for the book/story?
What's standing in their way of achieving this goal?
(in the case of novels, also ask the following)
What else happens during the story that my main character is going to have to address? What are their minor goals?
What's standing in their way of achieving these minor goals?
(and this doesn't even begin to dive into all of your minor characters and what their goals and obstacles might be...another blog post entirely)
If you're having trouble answering any of these questions, I wholeheartedly suggest that you start brainstorming answers and begin rewrites to incorporate them. Your story/novel will be greatly improved for it...