Death is the answer to life, the final summons for the jury-duty of the afterlife. One truth of fiction is the average novel has more death than a battle between clashing ethnic clans in Sub-Saharan Africa. Writers are obsessed with it.

The beauty of doing it creatively is most deaths you create will have as much forethought put into them as only serial killers can execute.

Meet your writing soul mate!

 There are a few keys to stick to when murdering a character. Remember that murder is most often a crime of passion, so there's little forethought put into it. Nobody plans to beat their husband to death with precisely 57 hammer strokes just for forgetting to buy ketchup, it just...happens. In that case it's just the straw breaking the camel's back, there's been years of arguments and build up. This means you must know the beast, or in Nietzsche's terms, ask the abyss to sit down to tea. 

First, know your killers.

There will be a test on this later

No, don't study them too in-depth unless that's a plot point. I mean know your types.There are:

1. Serial Killers - socio- and psychopaths who kill  selected targets for pleasure 
2. Spree Killers - sociopaths who kill random people in one burst after a psychotic break
3. Familiar Killers - people who kill  people they know for passion 
4. Byproduct Killers - people who kill as a result of another crime, such as shooting a cashier in a holdup
6. Motivated Killers - people who premeditate murder for gain, primarily financial 
7. Assassins - people who kill strangers for money

Now those are primarily my terms, but they are good groupings. You have to know these types and figure out what belongs in your story. For example if your protagonist is with the FBI they are concerned with serial killers, spree killers who cross state lines, and assassins who do the same or work for organized crime. An FBI agent would never be called in on a familiar killer case unless he was interested in the victim or perpetrator for a different reason. A private detective would not be called in on these cases, but would on the others when they became cold cases. Know the difference, or it can get awkward.

This man has no place in chick-lit, except at the author's house

I've talked a lot about murdering characters based off real people I know. The evil roommate who stile the microwave, the cashier who keeps calling me sir despite the fact no one else on earth would mistake me for a man, and so on and so on. In my fantasies they die slowly in a room that looks like a co-op shared by Dexter and PeeWee Herman, but such a murder would only happen with a whimsical serial killer. And have you ever heard of a whimsical serial killer? Did the Zodiac Killer or Jack the Ripper send Sudoku to the newspapers and police? Google it though and you find a hit...a novel, based presumably off 0 minutes of research.

If you're keeping to reality, and believe it or not writers of fiction should strive to, don't...just...don't. Serial killers are the result of severe emotional, physical, and sexual abuse, their IQs are generally high but not always, and they live quiet, obsessive lives filled with pain and agony. 

I see your pain and agony and raise you...Parent/Teacher conferences!

There are always exceptions to the rule, but killers are not the kind of people with normal hobbies. Their fantasies are fevered and dark. Few perfectly normal people pick up a knife and kill a family member, or meet a hot chick and kill half the town with her just because they saw a movie, or somebody did her wrong. 

The point is to start with the plot, working backward. What do you need? Is it a mystery with murder as the plot, killer unknown? Is it a drama about tracking a killer, identity known? Is it about survivors in the wake of a crime of passion or opportunity murder? Is it about an assassin clashing with whatever Hollywood stereotype is hot?

Assassin Zombie? I smell a sitcom! ...and rot. Okay, a CBS sitcom!

Let the plot dictate the type of murderer you need. Always pick the killer first. Even if you're not writing a mystery, write it like a mystery: write the crime first, then the aftermath/investigation. When they speak of writing backwards, this is what they mean.

The crime determines the killer. Most killers try to evade capture. Most uninformed killers try to hide the body (completely misunderstanding the writ of habeus corpus with wacky results), and serial killers often do, but spree killers, byproduct killers, and most assassins don't. Hitmen, a subset of assassins who work steadily for one organization, do. 

Jimmy Hoffa? He went out for a packa smokes, he'll be right back.

It's best to be informed, but at the end of the day know that most murders are brutal, quick, efficient. Passion killrs with remorse turn themselves in or kill themselves, but for the most part all killers try to hide the crime, make it appear as an accident, or flee. Serial killers like torture, rape, and necrophagia. No victim has a really humorous death, so if that's your aim go for an accident. 

Remember the basics: what kind of story are you writing? This will tell you somewhat what kind of killer you need, but the next question settles it. What kind of death do you need? Now that you know, study up on that type of killer. Who are they? What's their modus operandi? What real-life killers are similar, and what is their story?

Now, write the crime first, then put it aside, and write the story. It's a simple science, and sadly crappy fiction is full of people who did only the first step. This how you get Sudoku killers, singing telegram killers, and the like. Keep it logical and have fun. Want a creative death? Go for an accident or manslaughter. No real killer will accidentally pierce someone's heart with a rubber chicken launched from a potato launcher, but a neighborhood kid could, and be scarred for life, making for a great future as a flawed protagonist.

Or a bright future in prop comedy