How can a writer keep readers interested?

Have a compelling main character with goals and flaws? Have a cunning villain who opposes the hero at every turn? Create a fleshed out world that changes and reacts to the characters’ decisions?

All of those are good starts!

How about killing a main character? 

Gasp! That’s too far. After all, we put dozens, or even hundreds of pages into developing this main character and getting the readers to care about them. It’s not even the end of the book, we can’t kill them now!

How about this random character that got introduced a page ago? 

Much better. They can die if it means raising the stakes.  Lord Farquaad would approve.

Let’s look at this exchange another way (possibly dating myself with a Star Trek reference in the process): Captain Kirk, Spock, McCoy, and Ensign Ricky are beaming down to a hostile planet. Guess who’s not making it back alive?

If you’re young (or missed the reboots) and aren’t familiar with Star Trek: Kirk, Spock, and McCoy are three of the main characters that we follow through every episode. Ensign Ricky is wearing a red shirt and is lucky to even have a character name in the credits—he might as well be ‘random mook number two’.  Star Trek is also where the term ‘Red Shirt’ comes from. 

Basically, “Red Shirts’ are the enemy’s ‘Canon Fodder’. These are the good guys that get mowed down by the enemy to make the enemy look more dangerous and for us to worry about the safety of the main characters. 

It might not be the most honest way to raise the stakes in a story, but it works well as long as it’s not done ham-handedly. Ever watch a cop movie and the older cop beefs it (you know, the one two days from retirement)? That’s using Red Shirts. 

So, where have you seen this trope used? What’s an example of this trope being used well, or not so well?