Characters appear in writing of all kinds, even non-fiction, and often the characters in a piece of writing are what most attracts or repels readers. There are almost as many ways of creating characters as there are writers, but every writer can learn something from what other writers do.
Oliver at Literature and Libation has put together a blog post on character formation that is entertaining, informative, and brilliantly illustrated. Even if you glean nothing to use in your own writing practice, reading this post counts as time spent thinking about writing. (It’s likely to improve your blood pressure as well.)