If you have different characters in your story, you need to get a clear picture of them to present to your readers. Readers need to really see your characters, and get a feeling of what makes them who they are.
Writers sometimes give characters one particular characteristic, so it makes it easy to recognize them: eg one boy who always makes jokes, or a girl who always knows the answers in class, or a man who is always complaining about things. This is one way to make your characters distinctive.
Another way to develop your characters is to write a little description of your character for yourself, not to put in your story, but just so that you know your character well. Here are some questions:
• In terms of their appearance, what is one positive feature? One negative feature?
• What is their greatest secret fear?
• What is their greatest hope?
• Where do they live? How do they feel about where they live? Where were they born?
• Who do they feel closest to? Why?
• Which relatives have played a big part in their lives – in a positive or negative way?
If you really think about these sorts of questions for your character, even a character who is not so important in your story, then your reader will get a good picture and enjoy your story even more.