Characters are arguably the most important element of a story. So how do you write fascinating characters? Hell, how do you even come up with a character? Sure we know that most stories need a good guy, bad guy, and maybe a love interest but when should you add the rest of the people to fill out your world, and how many should there be?
It is a good idea to brainstorm when you reach the point that you know that a character is going to be reoccurring more than just a paragraph or two. Take a piece of paper and write down the characters name at the top and write down everything about their appearance on the left hand side of the paper. Next, try to find a logical reason as to why they look the way that they do and write the reason on the right side of your paper. Let’s say that your character has blonde hair and blue eyes. What does blonde hair symbolize? Are blue eyes common? As you begin to flesh your character out you will learn about their life and thus their personality. Find one or two details to exaggerate. This is used to make the character distinct from the rest. This is often done with eye color, but can be done with their personality too. An example would be to make your character incredibly happy all the time. The emphasis will make it easier for reader to recognize, and help create a unique voice for that person.
Stories are filled with people. How many of them become important, is entirely up to you, but I will use a little bit of psychology to help determine a number. Everyone has long-term and short-term (working) memory. Every piece of information we receive begins in our working memory, but only some is transferred into our long-term memory. On average most people can hold seven completely different pieces of information in their working memory at one time. Daily life often takes up some of that space so if a reader sits down to open your book they most likely have other things on their mind too.
Using this information, you should never have more than seven major characters at one time. This includes your protagonist, antagonist, and love interest. If you have more the reader can start getting confused. The longer that you write, the more characters you can add, because you can assume that some of the earlier characters are now living in the reader’s long term memory.
You can add minor characters as often as you like. One rule that I use is that if they are not 100% necessary to the storyline, they do not get a name or backstory. It does not matter that the Barnalbee the Shopkeeper has four daughters if he is only going to be seen in your world for twelve seconds. You can have an unlimited number of these people because they are easily forgotten.
You should try to introduce the main characters as early as possible. Don’t overwhelm your reader with every important person at once, but sooner is always better. These are the people you want to get attached to or hate. So the longer that you can spend with them, the more fulfilling your story will be.