Really helpful advice from Janis Hubschman's blog:

1. When the story stalls, ask: what is the character thinking now? Is she thinking anything? If not, why not? Characters need to learn something about themselves, about their values and assumptions.
2. Characters reveal themselves under stress. Raise the stakes. Drive the character into a tight spot. What are the psychological crutches the character relies on under pressure?
3. Readers like to learn about something when they read. The details of an unusual job or hobby, the day-to-day activities of a particular place at a particular time in history, for example, draw the reader in.
4. Trust the reader. Remember Hemingway's iceberg theory: "you could omit anything if you knew you omitted it and the omitted part would strengthen the story and make people feel something more than they understood."
5. Take apart successful published stories (or the stories of writers you admire) to see how they work.
6. Give the character something to do in the scene. It brings the character and the scene to life. A character soaking in the bathtub, thinking about her rotten marriage is boring. A character performing brain surgery, thinking about her rotten marriage is a different proposition.
7. To gain insight into a character, consider her history: Think about what happened before the story, what tortuous path led the character to this particular moment?
8. Allow the character to misinterpret another character's words or actions. In life, we often misread a situation, jump to conclusions. Interesting things can happen when characters make presumptions or project their own hang-ups onto others.
9. Let the characters connect with others. Alienated characters, the whiney and self-absorbed protagonists that blame everyone else for their predicament have lots of precedent in literature, but can hold readers at a remove.
10. Build tension by slowing down a scene. Let the scene unfold moment by moment. Linger on the details. Build silences into the dialogue.