Review your story plot for information you think could enhance or limit your character theme. If your story takes place in a specific time or location, it can limit the number of traits allowed to your character. If the story takes place in a high school, for example, the age range of your character is limited depending on the role he plays in the setting.
Write down the base information for your character such as the age, gender and name. Picture the setting of your book in your mind. From there, determine how well you want your character to fit into the settings.
Write a brief physical description of your character that corresponds with the setting of the book. Consider whether you want your character to fit in with the surroundings just like any side characters or if you want them to look out of place. For example, if your character resides in the Middle East, chances are he will have a dark complexion and similar clothing to the people around him unless you decide otherwise.
Write a description of your character’s behaviors based on their actions. For example, you can’t introduce your character as someone who is outgoing and arrogant if you want him to be shy. Once you determine the behavior of your character, it is easier to determine how he will affect the storyline.
Create a detailed background for your character to explain why he is the way he is. For example, write a back story about his family as well as his relations with close friends. This helps you create a more solid theme for your character, which is important when creating a believable storyline with a consistent character.