A coincidence that arises organically from a solid plot.
HOW TO DO IT: Mystery writers are constantly tempted to solve a plot problem by putting in a coincidence. After all, mysteries tend to have complex plots, and complex plots are challenging to write.
A description based in unconventional comparison.
A red herring that’s built into the plot from the get-go.
Dialogue that arises from action, emotion or necessity.
“You! I vould never had had you in my house if I had known it …”
“What’s wrong with the order? It’s for charity and good fellowship. The rules say so.”
“Maybe in some places. Not here!”
“What is it here?”
“It’s a murder society, that’s vat it is.”
McMurdo laughed incredulously. “How can you prove that?” he asked.
“Prove it! Are there not 50 murders to prove it? Vat about Milman and Van Shorst, and the Nicholson family. … Prove it! Is there a man or a voman in this valley vat does not know it?” …
“That’s just gossip—I want proof!” said McMurdo.
“If you live here long enough, you vill get your proof.”
Sidekick: “How come?”
Hero: “Because we’ve got to sabotage that convoy!”
Sidekick: “You mean the one that’s carrying 40,000 gallons of deadly radioactive bacteria straight toward the vulnerable entry point in the New York City water system?”
Hero: “Exactly! Yes!”
Characters motivated by almost unbearable forces.
“Um, see, he wants to keep the streets safe.”
Wanting to help strangers may be a plausible motivation for lying, but not for murder.