1. Be completely asexual.
Love? Pfft, you’re much too busy being intellectually superior to the masses to worry about things like natural human urges. You came out of the womb at 74 anyway, and everyone knows that people older than 30 don’t deserve love.
If your name is Tommy or Tuppence, you’re the exception that proves the rule. However, you’ll only get one installment where you’re “young,” and by novel two, your hair will have gone totally white and it will be pretty clear your relationship is only based on a mutual fascination with crime.
2. Be adept at fabricating logic out of nothing.
Someone stares at a painting for a moment too long. You notice a bitten nail amongst nine other filed ones. If these things don’t set off your little gray cells, then maybe you’ll have better luck in a Mary Higgins Clark novel. Within five minutes of being summoned to the crime scene, you should know who the murderer is (bonus points if you haven’t met them or learned that they exist), their top five likes and dislikes, their birthday and Zodiac sign, and why they committed the crime.
Of course, you’ll keep this all to yourself for the next few months while they gradually knock off other people who get too close.
3. Know how to craft and deliver a stellar monologue.
You must have all the building blocks for creating a monologue about whodunnit. You’ll need to have really excellent creative writing skills because you’re developing the narrative based on zero evidence—so your story had better be colorful, even if it’s not supported by facts.
4. Have zany quirks that people find odd but come to realize are just signs of your genius.
Is your head kind of egg-shaped? Are you a huge (old) gossip? Do you have a touch of OCD? Welcome to Agatha Christie’s novel.
5. Always, always be condescending to the paid detectives.
One of the best tactics you have in your arsenal is to pretend to be confused and batty while the Scotland Yard detectives slowly, clearly misexplain everything to you. Don’t worry — in the end, when you deliver your monologue, they’ll realize the cunning genius you are.
Alternatively, you can just be straight-up rude to Scotland Yard, even if they called you in to consult on the crime. After all, they only do this for a living, and you have decades of spotting jagged fingernails under your belt (many decades because you’re old).
6. Only consult on the really creative crimes.
If someone was shot point-blank, this is not the case for you. On the other hand, if the victim was shot point-blank and then artfully surrounded by clocks of different shapes and sizes, by all means, dive in. Keep in mind that the corpse must be dressed to the nines, however. No poor murder victims for you!