Two Things Not to Do
First, you should do your research. This is remarkably easy with the interwebz. In a twinkling I can find the name of a good restaurant in Aruba, or the best place to stab someone you wish to silence quickly. Gold, man.
But there are two things you should be extra-special careful about, especially if you are writing mysteries or thrillers. Cars and guns.
People flat-out love cars. They are protective of auto images in fiction, and if you make a mistake, they will WRITE IN AND LET YOU KNOW. If you can, run car details past a car nut, if you know one that won't get you involved in a long disquisition about the differences in Positraction and Equa-Lock.
I don't. I miss Tom Deitz, who passed away a few years ago and who would tell you in detail why such and such a car could not take off with a squeal of tires. But double-check your cars.
And double-double check your weaponry. I'm not much of a shooter myself, but I've got a relative who is retired from law-enforcement. When I was looking for a good sidearm for Jim Dallas, he said, "A cool one would be the old Colt .38 Official Police revolver. It's about the only series of revolver that has a safety."
He also explained that it's outmoded today because of the relatively wimpy caliber - but former cops love these things, and in the hands of a good marksman, they're as good as a 9-mm in stopping bad guys.
Okay, so I chose that one. But what he didn't tell me was that the Colt positive safety is not something you set. It merely has a block that prevents the hammer from striking the primer unless one pulls the trigger.
So in Cuban Dagger I had some throwaway line about the safety being "on," when it's not something you turn on or off. A reader pointed out the mistake, and I have since corrected it. That's a case of knowing almost enough but not quite.
Moral: Quadruple-check your gun research. Because, like car fanciers, gun fanciers are knowledgeable and protective of their favorites.
But...they are armed.