Tears and tea with Satan (Aka. How to kill a character) 

I'm sure everyone's heard the saying that if your plot is starting to drag you shoot someone (A character, please don't shoot a living human being.). As lovely as that may sound there is a right and wrong way to kill a character. 

Wrong:

Your plot is stuck. Sarah's life has gotten boring and she's already dealt with being bullied and the betrayal of one of her best friends. Then, after scrolling Pinterest for a few hours you find the perfect prompt. Maybe it's a quote from another book or maybe it's one of those TFR's writing prompts I love so much. And you decide to kill her brother. A car wreck, overdose, murder, all of these could work in killing off a side character to create another obstacle for Sarah to overcome. 

So Sarah gets a call on her cell phone while she's hanging out with her love interest who then has to help her through the trauma of her brother's death.

 Everyone dies for a reason. Don't simply shoot someone because your plot is drying up. Unless your character's emotional characterization or their plot line will be furthered by their death then there is absolutely no reason to kill them. Your secondary character's life is not simply a plot device, unless you treat them like real people and not simply background characters you will find that your readers won't appreciate your protagonist in the same way due to the fact that they have no real connection with anyone around them.  

Instead try: 

Sarah has struggled to come to terms with the betrayal of her best friend but when Mikala's brother and Sarah's ex comes back into town the two are forced to join forces to avoid the inevitable turbulence to come.

or if you desperately want to kill someone:

After her friend's betrayal Sarah is shocked to hear that Mikala had committed suicide after suffering from bulimia and depression for nearly three years. Sarah now has to come to terms with the fact that she believes she could have helped Mikala through her struggles if she had payed closer attention. 

Wrong:

Everything seemed to slow to a crawl as Markus watched the sword run through Lydia's stomach. She froze, unresponsive as the cold steel dug deeper into her core. He didn't even remember killing her assailant until he knelt beside her, cradling her head on his lap as the battle raged around them. She gasped for breath, 

"I - I love..." she took one last shaky breath. Then nothing. 

Instead try:

Markus stared around the battle field in relief. 

"We won." He said slowly, as if he himself couldn't believe their luck. 

"Sir... It's Lydia Sir. She..." The aid stuttered, trying to find the right words.

"Where is she?" 

The aid took a deep breath. "She's dead." 

In war people die. It's a fact of life. No amount of special abilities will keep your Protagonist's friends safe on a battlefield. You can describe the horrors of war, the death, the destruction. But no one will ever believe you if all your characters come out safe. There are no pauses in a battle, no dramatic goodbyes where your protagonist watches their best friend stabbed through the abdomen and then holds them as the life drains from their eyes. The fight doesn't stop long enough for heart wrenching scenes. If they die they die. 

A character's death can make or break your book. And wether their death is memorable or not can determine how your readers remember your character. 

John Flanagan did this beautifully in his book Halt's peril the 9th book in his Ranger's Apprentice series (which I highly recommend): 

Spoiler alert

Chapter 35 

The sun had risen more than an hour ago. It was going to be a fine day, but the group stood around the low mound of fresh-turned earth with their heads lowered in sorrow. They had no eyes for the fine weather or the promise of a clear day to come.

Head bowed, Will drove a wooden marker into the newly dug earth at the head of the shallow grave, then stepped away to give Horace room to smooth the last few shovelfuls of dirt into place. Horace stood back as well, leaning on the shovel. 

"Should someone say a few words?" he asked tentatively. Malcolm looked to Will for an answer, but the young Ranger shook his head.

"I don't think I'm ready for that."

"Perhaps it would be more appropriate if we just stand here quietly for a few moments?" Malcolm suggested. The other two exchanged places and nodded in agreement. 

"I think that would be best," Will said. 

Spoiler end

I have to admit that out of all the scenes Mr. Flanagan wrote this one struck a major chord with me. It is still the clearest in my mind. In fact I had to re-read it quite a few times to make sure I was reading it correctly. And it hurt. He took one of my favorite characters and slapped me across the face with their death. But out of all of my favorite scenes this is the one I remember. Why? Because he took a character no one thought would actually die, and killed them in a way that they didn't deserve. That is how you kill a character. 

And to answer the age old question of "Do authors cackle and sip tea with Satan when they kill their characters, or do they sob manically like the rest of us?" I'd have to say both. We sob manically while choking on our tea. It's a writer thing.