|No time to go walking in the woods!|
Opening that tin trunk in the attic.
Taking a short cut through the woods at twilight. And certainly not in high heels. (This tends to be largely, but possibly not exclusively, a female characteristic.)
Reading that old bundle of letters you found in the tin trunk in the attic.
Going back to the small home town and digging into that 20 year old unsolved murder.
Re-opening any cold case involving an unsolved murder, a disappearance, an unexplained/suspicious death, crime in general. Come on, you know someone out there is not going to take it kindly!
Entering any room in a house where the lights have inexplicably failed - especially the cellar.
Entering the cellar at all - particularly at night, when alone in the house.
Believing that just because the serial killer has been caught that the mayhem is over.
Not checking the petrol level in the car (that's gas, for my US readers) before setting off on that journey to that creepy remote cabin in the woods. You can add checking the weather forecast to that.
Going to the remote creepy cabin in the woods at all. Ever.
Drinking/eating anything in the company of a chief suspect.
And for the villain - telling the hero/heroine all about how clever you are and how the crime was done - don't you know that's the end of the book and your downfall is nigh?
Of course, if the characters listened to any of that, stories would be a lot thinner on the ground.
So, it's a good job they never do.