Back to how to make your characters live. When revising, you should be looking to make sure your characters are believable, distinctive and consistent. What does this mean for the writer?
For a character to be believable, there are two steps. First the writer needs to walk in the character's shoes. Becoming the character can make people look at you strangely and wonder if you belong in a padded cell but this does work. Sit down and close your eyes and become this person you want to show the world. Imagine how they would react to any given situations. The second part of this is after you've written the things you as the character have done or said to look at this from the outside. Does what you've written made sense. If so the character will be thought as a real person by the readers.
The second thing to consider is distinctive. What makes your hero, heroine, or minor character stand out from the thousands of other characters. Do they have a particular kind of speech. Is something very important to them that puts them apart from other characters? Is this an essential character. What tastes in food, dress, speech, action do they have. One of my characters has a liking for mint tea and grows her own mint and makes tea blends. This love of mint tea has carried through four books. She even packed teas when she traveled across the country. When the reader picks up one of her stories they recognize her as unique.
Consistency is another thing to consider when you're revising for character. Does he or she lose their temper when certain actions are seen or words are heard? Does this always happen or is it hit or miss? If the character acts in a different manner the writer needs to be sure the change is explained and made to look believable or the reader will put the book aside and not read more.