You kill a character, drive them away, push them out of scene - make sure they are missed.
If the reader doesn't care that you got rid of them, what the hell were they doing in the story?
Think about that a minute. I'll wait.
There is a great deal of narrative tension to be wrung from our "throw away" characters. Chandler and Hammett did it well: the nobody with whom we are intrigued for the short two pages they are in the prose.
They leave and we miss them.
I've been listening to T Bone Burnett lately. I especially like his song "Humans from Earth" for its vague threat. You have to know us humans to know what T Bone is suggesting in the song but then, you know us, too.
What strikes me about music that T Bone produces (he's a top end producer) is that when the song is over, you miss it.
So, you need a ticket-taker, a beat cop, a homicide detective, a receptionist, a mother-in-law. Please, make us miss them when they're gone. We're reading. It's the least you can do.
I'm off and you'll miss. I'll leave some pages for you, though. I'll leave pages.
You should leave some too. They don't write themselves, you know.