I have been a BETA reader for a few authors, and have edited a couple of novels and the biggest mistake that I find is people do not accurately describe or make you relate to their characters.
For example, you want us to love a character and hate another so we have an emotional reaction to the outcome of the book. I love books where I feel like I am friends, or I know these people personaly. Which is why you definitely need to do a character chart on your characters. For example this download here:
This makes you think about the structure and the background of the character. You dont want your character to do something out of character in Chapter 4 that doesnt seem like the character in chapter one. You want to have a clear backstory so that you can always keep up with this person as if you the writer knows this person in real life. Make the characters real people before you write too much about them. Give them a real life story and hint at it or tell in the story.
Now Im not telling you to write a chapter on the backstory, but your character flaws and personality should always come out in the way you write about them. It should be painted in the words you use and their conversations.
Make sure you use discriptions and really flush out your story. Watch this video:
Until next time… happy writing!