So you've finished typing up that prized manuscript, and you've sent it off to one of your dear (honest) friends to get their opinion. But what if they decide that something is missing or not right in the story? Do you rewrite the whole thing?
Truthfully, the answer is sometimes. If it's your first draft (or your first novel), you'll probably want to rewrite it multiple times as you grow and learn as a writer. Taking writing courses helps with this—but what helps even more is to keep writing. The more you write, the more you grow. Practice makes (near) perfect, as they say.
But sometimes, even after you've polished up that manuscript to within an inch of its life, your dear friend still says there's something missing. What do you do then? Well, if they are specific, dissect that manuscript and fix what they think needs fixing (assuming you, as the author, agree). But if your reader isn't able to pinpoint the something that is bringing down your story, there are a few things you can try:
1) Make a chart of your main and minor characters and their characteristics.
List things like appearance (eye and hair color, build, etc.), personality (likes, dislikes, pet peeves, fears), and speech patterns. When reading through your manuscript make sure that each character behaves as they should.
2) Make a flow-chart of subplots.
And make sure each of these has closure. Leaving these open-ended can sometimes disturb the reader. Even in a series you need the closure of adding an extra "We haven't found what we're looking for...yet." That way the reader doesn't expect to know until the next book what happens. But if you leave it open-ended, they might start to wonder.
3) Write all the tones/themes in your book on sticky notes.
Then stick them to the wall, the computer monitor, what have you. One at a time, search through the manuscript and examine the symbolism you have to go along with each theme. This is often done unintentionally, but if you find something missing, something that might accentuate that theme, add it.
Conversely, write down the tone/mood of each scene. When reading through it, make sure the sentence structure, etc. matches and conveys that tone. If the character is angry or afraid, there will be short, direct sentences. In a love scene, there might be more flowery prose—certainly more description!
Those are the top three things that I find help me to organize and flesh out my characters. What about you? What are your tricks?