When I sold my first novel, BOUND TO TRADITION trilogy, to my German translation publisher, one of the comments I got back from the editorial team was: "The pace for this novel was perfect – never too fast nor too slow."
I was surprised, because I'd never thought much about pace. Certain things come easy to every author, and other things come hard. Pace comes easy to me. When a paragraph or chapter drags along, I somehow sense it when editing and revising. Most writers do, especially when you read your own work as a "reader".
What is pace?
It's the amount of time you spend on each part of the story. The Goldilocks Principle applies to pace – it should be neither too fast nor too slow, but just right. There isn't any tidy little rule you can memorise to define what the perfect pace is for a story. A general rule is to vary the pace to suit the tension in the scene. So most often, you'll want to zip through the boring parts of the story and take more time on the exciting parts. That seems very strange, right? If you're showing a high-speed car chase, surely you'd want to make it read fast, wouldn't you? Which means using fewer words, right?
Yes and no.
Yes, you want it to read fast. But no, you don't want to spend fewer words on it, you want more. There's really no paradox here. Think of a football game in which one of the players makes a huge play, dodging first one defender, then another, all the way down the field, finally dancing into the end zone for a score. What happens next? You can bet your manuscript that the networks are going to show the whole thing AGAIN, this time in slow motion, dragging out every twist, turn, footwork a la Ronaldo, and all the way down the field. Showing it in slow motion takes a lot longer, but it doesn't cut the pace. It INCREASES the pace.
Why?
Because when the play ran at normal speed, you missed most of the action. You saw a fellow running with the ball and you saw others missing to stop him. It all went by in a blur so fast that you couldn't take it all in. When they ran it in super slow motion, you saw every little move, every tensing muscle, the bunching and flapping of the shirts and shorts, facial expressions and the movements of the muscles. You saw the defence response fooled and beaten. All the way to the kick, ball sailing through the air, the goalkeeper's twists and turns to stop the score, and finally the ball hitting that particular part of the net, perhaps (and more exciting) hitting whatever part of the posts first before sailing into the net. You saw every block, every weave. You saw the last desperate flying ball just an inch from the keeper's fingers or a breath above his head to land the score.
And then the normal pace resumed.
It took ten times as long to see it that way, but this time, YOU SAW IT ALL. You saw every action, every reaction, in beautiful, sharply cut detail. That's what you came to see or turned on your TV to watch. In your novel, the moral equivalent of super-slow-motion involves spending far more words than you normally would, but using much shorter sentences and shorter paragraphs. You alternate rapidly between what your point-of-view character is doing and what his opposition is doing. If your paragraphs are normally three sentences apiece, they might drop down to two sentences or one.
If your sentences are normally ten words apiece, they might fall to five words. Or three.
Or one. Or, in dialogue, by certain omissions. Here's an example from the first book of my DARK DESIRES trilogy. (To explain the background, Moni and Marie are best friends, Marie has just broken up with her boyfriend Roman, Susanne/Susi is Marie's younger sister, and Northern Light's is Marie's curio shop):

Moni had given her the cat at lunchtime. She simply walked into Northern Lights, bearing the cat in its basket and then hauled in a month's supply of Sheba. Susanne was all gone on the cat and cooing while Marie eyed Moni.
Moni said defensively, "You've taken to holing up here or in your flat, love. Here's some female company, since you avoid even having lunch with me."
"Then you should have brought me a puppy."
"You're not particularly fond of dogs, I remember," Moni cocked her head.
"What's her name?" asked Susanne, her faced buried in the cat's fur.
"She's open to options. Personally, I love Sheba. Just so Marie doesn't deviate from its favourite menu. And that's been its name since kitten-hood."
"How do you know its favourite menu?" asked Marie.
"Let's call her Romana," said Susi.
"The pet shop," said Moni.
"Have you gone mad?" screamed Marie at Susi.
"Okay, sorry, sis. Ginger, then?" The cat was.
"Got to scram, love," Moni gave Marie pecks on cheeks. Marie kissed the air around her girlfriend's cheeks back, and Moni headed out.
"Bye Moni," waved Susi. "Ginger?" she repeated to her sister.
"Ginger has whiffs of competition. I'm blonde. Sheba." "She goes for exotic competition," Susi informed Ginger/Sheba.
Marie picked up a teddy-seal key holder and threw it at Susi, both shrieking.
"I want a worthy competition!"
Ginger remained Sheba.

Notice how repeating the Big No-No "said" changes the pace. And without going into all the details about Moni worrying about girlfriend Marie's recluse nature, deciding to do something about it by going to the pet shop to buy Marie the cat, then choosing the cat's age and gender, and then going to the supermarket to buy the cat food, and finally bringing all that to Marie at Northern Lights, all the way to giving the cat a name, I've compressed the scene tight. I've brought all that into the reader's mind in clipped dialogue and abbreviated explanations.
(By the way, avoid such long sentences as the one above!) You can't keep that up very long, of course. That would be crazy. In the same way, it would be crazy to watch an entire football game in slow motion. You want to ramp up the pace only for the high-tension scenes, where the stakes are high. Slowing down the pace works the opposite way. Longer sentences. Longer paragraphs. Fewer actions and reactions. More interior monologue, longer dialogue. Why does this work? It's really very simple. The reader reads fiction hoping to have a Powerful Emotional Experience. Inside a scene, you provide this by showing actions and reactions between your point-of-view character and the other characters. Every time you show your POV character reacting to the other characters, you have a chance to provide an emotional hit point to your reader.
If you have short actions and short reactions (using short sentences and paragraphs), then you score emotional points with your reader faster. If you lengthen out the actions and reactions, then you score fewer emotional points. Naturally, it only makes sense to speed up the pace when the tension is high. If you try this when the tension is low, the story is going to drag. (Imagine showing the team's pep-talk huddle in slow motion!) There are an infinite variety of paces you can use as you work through each scene. You speed it up and slow it down, possibly several times in the scene.
How do you know when you've got it right?
That's easy. You've got it right when it feels right.
Fiction is about creating a Powerful Emotional Experience in your reader. Tweak the pace until you're doing that, and your reader will feel like Goldilocks.
Glorious pacing, fellow writers!