Know your character. Really. You can't expect to include personality in the book if you, the author, don't even know what this character is like.
How do you get to know your character? Start off with the character bio I included in another chapter. (If you don't feel like retyping that whole thing, send me a private message and I can send it to you so you can copy and paste.) Really develop their attributes and their flaws so you are fully accustomed to them before you try to write them into your story
Know what their favorite things are, what their fears are, what their type of guy/girl is. I'm not saying write these all in to the book, but as a writer, know your character as you know your best friend, and then you will be able to write their personality with ease.
Responses matter. Yes, they really do, because this shapes how the audience views your character. Is one of your character's attributes patience? Then, when their friend tells them they're going to be late, this character probably wouldn't blow up in their face. She might sigh a bit, but then resolve that it's not worth getting in a fight over, and that waiting a few minutes doesn't matter.
So shape your characters responses (not only to other people, but also their responses to circumstances, weather, and more) according to the personality you've thought up for them. With consistent responses, the reader will begin to know your character and how she/he is going to act.
The character's choices shape who they are. Are they wise? Or are they foolish and hasty? How your character makes choices, and also what choices they make are very essential to determining the character's personality.
This may come in to play if, for example, Mary asks Jane to come to a party.
If Jane immediately responds with, "Sure, why not? What could go wrong?" We'll know that Jane probably doesn't think through decisions very well or think about consequences.
However, if Jane hesitates, asks a few questions about the type of party, or considers possible outcomes, we'll know that she thinks before she acts and that she is a cautious person.
You see what I'm saying? Include the character's thinking process in their choice-making and we will begin to understand the way they think.
If Kate sees an animal on the side of the road, her first instinct may be to stop and help it. However, if Jack sees this same animal, he may just keep driving past without a care in the world. This may show us that Kate is an animal lover, or just cares for life in general. Jack, however, may have other priorities.
Background. Where does this character come from? What kind of family does she/he have? What kind of friends? Keep all this in mind as you flesh your character out, and know that different upbringings could result in drastically different personalities. You don't have to explain this all out in your book, but just keep it in mind so you make your character realistic. Perhaps her childhood situation explains why she is so cautious around certain people. Situations like that can reveal a character's personality as well as their background.
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Jessie's Tips for Better WritingRandom
I'll show you how to improve your story with just a few tips and exercises. Writing a novel can be confusing, especially if you're new to it. Even if you're a pro at writing, it still helps to be refreshed. This is my way to help you. Hopefully it...