Here are a few tips for novices and first time authors, more seasoned writers probably already know this stuff. First, always write down your ideas, bits of dialogue, or other inspirations – you won’t remember them for long so write them down immediately
Second, find a good editor and a proofreader. No you cannot edit your own writing. Sorry, but no. Even if you think you’re the next Ernest Hemmingway, Stephen King, or Mark Twain, you need an editor.
Third, Give each of your characters a clear and distinct voice, know your character before you add them into your story. Starting with the main character(s), profile each one.
Determine external features and internal mood, personality. Of course you have to know gender and age, don’t stop there, Give them a place of birth, have they moved?, What are, or were, their parents like, etc.