If you're like me, beginnings and endings to novels come relatively easy. Maybe a great opening scene and a bang-bang, satisfying to everyone ending take some thinking, but the general opening and closing of the novel are there almost from the inception of the idea. But, of course, more than half the novel is neither of these; it consists of the middle of the book. While I usually have a few ideas of how to bridge the gap, most of this chunk of the book is a mystery to me as I start planning. Thanks to South Park, I like to think of it as The Underpants Gnome Problem.
Sometimes this middle section of the novel seems like it'll never materialize. Little scenes come, but nothing major, nothing that will wow the reader. But fear not, there are things you can do to defeat this dreaded Underpants Gnome Problem. Here are a few things I like to do.
1) Freewrite: If you're not sure what comes next, simply grab a blank sheet of paper or open a new file in your word processor, and write. Don't worry about making much sense, simply jot down ideas that come to you. Keep your pen (or fingers) moving, and put down ideas that come to you, no matter how silly they seem. Sometimes those silly ideas turn out to be gold, either on their own, or with a bit of tweaking. Or those silly ideas might be blocking the golden ones. Whatever the problem, often freewriting will help.
2) Work on something else: Maybe your brain simply needs to marinate the idea. Work on a short story, watch TV or a movie, or read a book. While you're concentrating on these, your subconscious mind will be playing around with ideas for your novel. Give it a day or two, and then go back to it. You might find that you now have a nugget of awesomeness waiting for you!
3) Start plotting: You know how you want to start, so plot that first act. When you get to the final scene, you might be surprised to see you know where you want to go next. And if not, plot the ending. If you're still blocked, plot minor scenes from the middle, ideas that have been floating around but aren't those big blockbuster scenes you need to bridge the gap from beginning to end. Put all of these scenes on 3x5 cards and spread them out so you can see them at the same time. Chances are, something will click. You'll see ways to put these scenes together, and those big blockbuster scenes will come.
4) Know your characters: Get to know your characters. Often they will dictate how the middle of the novel should go. You know the major problems, so give your characters quirks that work with or against these problems in interesting ways. Your characters could very well be the key to getting your novel from beginning to end seamlessly.
If you try one or all of these tips, you should be well on your way to bridging the gap between collecting underpants and profit. That big dreaded question mark should fall away. Remember, whatever you choose to do, it can always be changed later, either while you're writing (there's no rule saying you can't amend your outline) or during revision. Since the middle is the biggest part of the book, it can be daunting, but these simple tips should help you out. So get out there, collect those underpants, and make a profit. I have no doubt you'll figure out how it works!