"GUIDES" The Writer's Guide (Character Creation and more)

Characters, Part I: What is the scenario, and why are they needed?

Hey! You! Spoilers for some books are in here. Referenced directly (with spoilers) is K. A. Applegate's Animorphs series. If you are past book 23, The Pretender, you are safe as the spoiler only applies to books 1 and 23, and The Andalite Chronicles. Spoiler start line is marked in all caps. Spoiler end point is marked in all caps (end of the paragraph). A small plot point for Anthony Horowitz's Alex Rider series is present as well, but is not marked as it does not spoil anything directly and makes no sense unless you have finished the entire series. Enjoy!

Introducing a new character is a common but complex event for any writer, whether they realize it or not. Maybe you find yourself with not enough to keep the plot moving forwards, or you're SICK of people shipping the two main characters just because they think they're lesbians (and you know they aren't, they just happen to be traveling together). Maybe you need a sudden guide to offer your characters a quest, or maybe this "ghost town" is just a little too... empty.
Three major things contribute to a character's need for existence and how they interact: scenario, surroundings, and other characters. These will all contribute to how a character is perceived, how they are welcomed, and the other characters' attitudes towards them.
Scenario is VERY important. Scenario can dictate when and why they appear, as well as who they are. Scenario typically matters most when you have a conflict, or when surroundings make things eerie. A character appearing in a snowstorm? Mysterious, and most likely a traveler or a stranded person caught in the storm. See if you can't find out why they were outside and unprepared. A character appearing during a fight might be friend or foe... make sure to expand on who they fight for and their initial actions in this case. A character offering advice because you stepped into a fortune teller's tent is another good example, bordering on both scenario and our second major factor, surroundings.
Surroundings is the second most important part. You know your scenario, but what are the specifics of the surroundings? A character is not going to appear out of nowhere. A character has to come from somewhere. Someone isn't going to sneak up on you and appear out of nowhere in, say, a loaded car on a long highway. But a loner roaming in an abandoned town? Not that odd. A stranger appearing at the mall? Expected. Remember to introduce new characters in a logical location. A stranger isn't going to wander into a submarine or a space ship. Your characters could be on either side of a surroundings-based encounter: either the unknown character appears from the surroundings, or your characters stumble upon the other character. Play that part of it based on what is more likely and who better knows the terrain.
Other characters form the third most common introduction method. A new character is introduced as a friend of an existing character, as a relative, or perhaps as a long-lost love. They might have known or unknown qualities off the bat, a reputation, relationships, and other information. This is arguably both the easiest and hardest way to introduce a new character. If done properly, it is a piece of pie. If done wrong.... it can feel rough and out of place. Generally, introducing an ex is only acceptable if you have two existing characters of the same gender.* Make sure to establish the connection right away, unless the link is hidden and crucial to plot. A good example of this (SPOILERS FOR ANIMORPHS (books 1 and 23)) is when we meet Elfangor in book one (The Invasion) and later find out he is Tobias's dad (book 23, The Pretender). This is also crucial to the plot of at least one other book^ in the series (The Andalite Chronicles). Properly done, this can be your greatest weapon. One of my own characters has a similar story, which will be a major part in determining his backstory at some point when I get ready to delve into that. Or, it may simply never come to light. We will see! END SPOILERS.

Overall, how you introduce each character will make an immediate first impression of how they are perceived. Never introduce a character too early, and never too late (we are looking at you, Anthony Horowitz, and directly thinking of Ash in the Alex Rider books). But.... never tell us all about them, either. We'll discuss why that is important next, in Characters, Part II.

*As a writer, I personally tend to stay out of the way of the gender debate. Gender is mostly mentioned in passing to explain body type.
^I am rereading the books (which I was named after!) so I'm not sure if it affects any others, as it has been too long since I last read them. I know it directly impacts those three I have listed.