2. Kill somebody. The more vital you think they are to your story, the better. Look at it this way: at least it will be a surprise.
2a. Kill somebody fictional, I mean. Although murdering one's spouse might sometimes relieve frustration, and there is plenty of time to write in jail, it's still hard on the kids.3. Go for a walk.
4. If that doesn't work, either wash dishes or take a shower. It's now known that inspiration is dissolved in common hot tap water.
6. Crib from a classic source. It was good enough for Shakespeare.
7. Explain the problem to a friend. This is especially effective if you can trap them in a moving car on a cross-country trip. Half the time, in the process of explaining it, you'll figure something out. Another third of the time, they will give you an answer in self-defense after the first three hours. If you attempt this technique in restaurants, be ready for extremely attentive service as the waiter tries to overhear where you hid the body.*
8. Find something to make worse, and make it worse. Do this over and over and over again. The technical term for this technique is "escalation."
9. Get out the manuscript that you have written and go through it. Outline it. For each scene, write down who is in the scene, what happens, and what changes occur over its course. What is resolved? What is worsened? What is established? What's the pivot of the scene? When you come to the end of the outline, you will have a handy list of everything the book is doing, so you can keep doing it.
10. Play repetitive mindless computer games for hours. Realize you've wasted the entire writing session and go make dinner. Watch TV with (unmurdered) spouse. Wake up at 2 am from vivid dream with a head full of plot.
11. Go through the manuscript (or your reverse outline) again, and this time figure out all the things that need to get done before the book can end. Write them down on notecards. Tell yourself that you will write a scene in which one (1) notecard's worth of problem will be dealt with. The write it.
12. Give the characters something else to do and let them explain the plot to you while they eat dinner or play poker or whatever. You can always cut this later. Go ahead and write it now.
13. Write differently. Switch to pen and paper, or write on tiny scraps of notepaper (not intimidating) or switch to the computer if you were writing longhand, or type it in a email to somebody who will only make fun of you a little.
*In the current climate of fear, we recommend not using this technique on aircraft or trains.
** because jonquil asked.