Me, me, I'm important, too - creating minor characters

Building on my theme of characters, remember that minor characters are important. Some may be so negligible that they won’t even get names but they are important, even if all they do is serve the pints or open the door.
Why? Because every single one of these people is designed to fulfil a brief role in the story, they all have a job to do.
For example they can reveal something about your main character -- someone who snaps at a chamber maid tells us a lot about themselves – or maybe their individuality will set a mood, add humour, make things happen; a scowling barman can do a lot for a scene. I use them all the time in my crime fiction.
Warning; if a character who isn’t supposed to matter starts distracting from the main thread of the story, either cut them out or figure out why you, as a writer, are so interested in them.
There’s nothing wrong with a background character attracting attention—as long as you realise that they are not part of the background anymore. The readers will notice them, too, and expect them to play a bigger part in the story.
 

John Dean