Novels need action. The type of action varies, but they certainly need some kind of action or your readers will fall asleep reading your book. Action is the core of your plot. Without action, there's no story. But just as important to the action is the pacing of your novel. These two elements make up the very basis of your general plot.
A Novel Needs Action
Your novel must have action at various points, but defining action can be a little problematic. Is action a car chase? Yes. Is action a standoff between your protagonist and your antagonist? Yes. Is action the thoughts running through the protagonist's head? Yes.
Action can be a lot of things, usually depending on genre and context. So let's define the action in a novel as anything that is important to the overall plot of the story. This could mean that the "action" in your novel includes your main character sitting at a bar thinking to himself. He might not be involved in a gunfight, but that doesn't mean something important isn't going on in his mind.
So, now that we've defined action, perhaps you can see how novels are built up of these little bits of plot. You don't need a gunfight or car chase on every page. But something needs to happens to further the plot.
Constantly throwing action at your audience, however, creates its own set of problems. You need to break the tension once in a while, but without letting the action stop completely. This is where pacing becomes important.
The Pacing of Your Novel
The pacing of your novel can be defined as the rate at which the action happens. This rate will be primarily determined by the type of book you're writing. A laid-back romance will have a slower pacing than an action-adventure novel, for example. But how do you convey this pace?
Start by classifying your scenes into two groups: tense and relaxed. If you're having trouble categorizing some of the scenes, create a third category: semi-tense. Once you've done this, space them out a bit. You probably don't want eight tense scenes back to back (unless you're writing a thriller or a horror). I write a lot of fantasy-adventure novels, but I'm careful not to pack too much tension into one section (except for the end). I vary the intensity of the scenes to keep the story moving.
Now that you've ordered your scenes, look at each tense scene and sharpen it up. You can add action, of course, or you could use the power of the written word. Short paragraphs. Sharp words. Tiny sentences. These help increase the tension in your story. Heighten the tension until its wound tight.
Then release it. Use longer sentences and larger words while increasing the size of the paragraphs. You'll be surprised at how this technique can increase or decrease the tension of a given scene. The words you use and their structure on the page should reflect the pace you're trying to convey.
Your novel should be like a roller coaster ride. Take the tension up and down as your story requires, giving your readers a break from the tension when required. Think about the feel you want to convey and work hard to make sure your take your readers on the journey with you.