Years ago I used to hold an annual first chapter of a novel contest on this website. During that time I read many good entries, but I also routinely encountered the same mistakes. Let me share a few:
Expository writing. Explaining the character and the setting for several pages alienates the reader. Open with a scene to engage the reader.
Back story. You don’t need to explain a character’s history for three pages. Weave backstory in little by little. Get to that opening scene, pronto!
Telling, not showing. Sammy looked guilty is not effective. It tells readers what to think, which lessens their investment in the story. Sammy avoided her stare shows us he’s guilty. Readers draw their own conclusions. They are engaged.
Weak verbs. Overuse of the “to be” verbs and other lightweight verbs makes for dull writing. Highlight these weak verbs and replace with muscular verbs to give your writing pizzazz.
Avoid these mistakes. Hook ’em from the start!