Warning: You may encounter some opinions.
Writing Myth: You have to start your story off in the middle of the action, or “In medias res”.
It is said (as I have heard from a number of English and Creative Writing teachers) in order to catch your reader, you must start in the middle of the action, or else it will not be interesting enough to get your reader to continue on. They will set the book down and look for another if you do not do this.
Is this true? No.
Although opening in the middle of the action is commonly used and can be very effective, it is not the only way to open, and other ways of introduction are not automatically going to lose your reader. In fact,  it matters very little what type of opening you use as opposed to how you use that type.
Success is not determined by starting off in the middle of the action. There are many ways to open a story. Whether people will be interested is based on how you execute it more than what type of opening you’re executing. And there are several ways to open. 
1. Introducing characters. J.K. Rowling’s Harry Potter is a good example of opening by introducing characters.

It starts off by giving information, in this case, about the characters. Not just any information, but interesting information. It shows the quirks of the characters that make them stand out among any other characters you as the reader have already been exposed to in other stories.
Important note: It also makes the reader wonder, how will this information play a part in the story? Don’t just give your reader an interesting fact about your characters and do nothing with it. That’s misleading and could make the reader lose trust in you as a story teller.
2. Introduce the setting. Setting is defined as the surroundings or environment of anything (X). Which means you are able to describe what the landscape looks like, or what the environment is like. What are the beliefs or traditions in the setting that will affect the character(s)? An example of this is seen in Diana Wynne Jone’s Howl’s Moving Castle.

Not only does it imply right off the story takes place in a fantasy land, but it states a belief the people have that will directly affect the main character. It could be interesting to know a belief that affects the fishermen, for example, but it focuses on what will play a part in the story over and over again.
Whatever you decide, take in to account what Neil Gaiman said. 
"You can take for granted that people know more or less what a street, a shop, a beach, a sky, an oak tree look like. Tell them what makes this one different."
3. Withhold information. You could start off by giving your reader a taste of what’s going on, what the setting is, who the characters are, while giving a hint that not everything is as it should be. Shirley Jackson’s short story, The Lottery, is a prime example of this.

At first glance, it seems like a normal day in a normal village. But as you read, you start wondering what the lottery is for. It’s not a typical one, because you would just have everyone get numbers and announce it. Why would it take so long and why is it taking place in individual villages? By taking something that’s recognizable and changing a detail about it, it makes the reader wonder what’s going to happen, or what’s off about the situation.
More examples can be found of how stories can start without beginning in the middle of the action. There are many other ways to introduce a story, and if you want more ideas or tips, you can go to these sites:
How to Start a Story (Used for the “Withhold Information” example)
10 Ways to Start Your Story Better
3 Ways to Start a Story
12 Ways to Open Your Novel
The point of this is, you do not have to start a story in the middle of the action. Many successful, as well as some of the most interesting, stories do not begin this way. It is not by any means a bad way to start, it’s just not the only way. What is important to capture your audience’s attention, is to introduce character and conflict in some way.
Also, when writing an introduction, do not try to get it right in the first draft. You have revisions for that. You can start writing a story where ever you want and come back to the introduction later. Just don’t focus on it so much that you forget to write the rest of your story.
———————
"One day I will find the right words, and they will be simple." ~ Jack Kerouac

Warning: You may encounter some opinions.

Writing Myth: You have to start your story off in the middle of the action, or “In medias res”.

It is said (as I have heard from a number of English and Creative Writing teachers) in order to catch your reader, you must start in the middle of the action, or else it will not be interesting enough to get your reader to continue on. They will set the book down and look for another if you do not do this.

Is this true? No.

Although opening in the middle of the action is commonly used and can be very effective, it is not the only way to open, and other ways of introduction are not automatically going to lose your reader. In fact, it matters very little what type of opening you use as opposed to how you use that type.

Success is not determined by starting off in the middle of the action. There are many ways to open a story. Whether people will be interested is based on how you execute it more than what type of opening you’re executing. And there are several ways to open.

1. Introducing characters. J.K. Rowling’s Harry Potter is a good example of opening by introducing characters.

It starts off by giving information, in this case, about the characters. Not just any information, but interesting information. It shows the quirks of the characters that make them stand out among any other characters you as the reader have already been exposed to in other stories.

Important note: It also makes the reader wonder, how will this information play a part in the story? Don’t just give your reader an interesting fact about your characters and do nothing with it. That’s misleading and could make the reader lose trust in you as a story teller.

2. Introduce the setting. Setting is defined as the surroundings or environment of anything (X). Which means you are able to describe what the landscape looks like, or what the environment is like. What are the beliefs or traditions in the setting that will affect the character(s)? An example of this is seen in Diana Wynne Jone’s Howl’s Moving Castle.

Not only does it imply right off the story takes place in a fantasy land, but it states a belief the people have that will directly affect the main character. It could be interesting to know a belief that affects the fishermen, for example, but it focuses on what will play a part in the story over and over again.

Whatever you decide, take in to account what Neil Gaiman said.

"You can take for granted that people know more or less what a street, a shop, a beach, a sky, an oak tree look like. Tell them what makes this one different."

3. Withhold information. You could start off by giving your reader a taste of what’s going on, what the setting is, who the characters are, while giving a hint that not everything is as it should be. Shirley Jackson’s short story, The Lottery, is a prime example of this.

At first glance, it seems like a normal day in a normal village. But as you read, you start wondering what the lottery is for. It’s not a typical one, because you would just have everyone get numbers and announce it. Why would it take so long and why is it taking place in individual villages? By taking something that’s recognizable and changing a detail about it, it makes the reader wonder what’s going to happen, or what’s off about the situation.

More examples can be found of how stories can start without beginning in the middle of the action. There are many other ways to introduce a story, and if you want more ideas or tips, you can go to these sites:

How to Start a Story (Used for the “Withhold Information” example)

10 Ways to Start Your Story Better

3 Ways to Start a Story

12 Ways to Open Your Novel

The point of this is, you do not have to start a story in the middle of the action. Many successful, as well as some of the most interesting, stories do not begin this way. It is not by any means a bad way to start, it’s just not the only way. What is important to capture your audience’s attention, is to introduce character and conflict in some way.

Also, when writing an introduction, do not try to get it right in the first draft. You have revisions for that. You can start writing a story where ever you want and come back to the introduction later. Just don’t focus on it so much that you forget to write the rest of your story.

———————

"One day I will find the right words, and they will be simple." ~ Jack Kerouac