The setting plays a big part in building the initial suspense of this story. Readers are told that the setting is the frigid wasteland of the Yukon. This is one of the harshest landscapes on the planet, so setting the story here easily heightens reader awareness of potential threats to the man that could be life threatening. The initial suspense is also heightened by placing the setting at night. The man is far enough north where he actually won't get daylight at this time of year.  

However, there seemed to be an indescribable darkness over the face of things. That was because the sun was absent from the sky. This fact did not worry the man. He was not alarmed by the lack of sun. It had been days since he had seen the sun.

Darkness makes everything more foreboding; it's why kids are afraid of the dark and like sleeping with a nightlight on. Dangerous and foreign things lurk about at night, and the man is in a place where it's been dark for days.  

A third thing that adds to the initial suspense is the fact that the man is alone. There is strength and security in numbers and/or having companions to travel with. A lone traveler is automatically at risk because if anything goes wrong, that traveler is guaranteed zero help. A life threatening situation is compounded by being alone.  

Perhaps the old man on Sulphur Creek was right. If he had a companion on the trail he would be in no danger now. The companion could have built the fire. Now, he must build the fire again, and this second time he must not fail.

The fourth way that London builds suspense early in the story is by telling readers that the man isn't an experienced Yukon explorer. This is his first winter. He has zero experience and knowledge of the area, the terrain, the cold, and the weather. He's ignorant of the potential threats that are around him all the time. Readers would be less nervous if we knew that he had survived ten seasons in the Yukon. If he had, we would know that he knows what he is doing; however, this isn't the case. We know that he knows nothing, and that adds suspense and makes us nervous. 

It was not because he was long familiar with it. He was a newcomer in the land, and this was his first winter.  

In this story, a man makes a journey across the frozen landscape of the Yukon territory, to meet his friends.  As a stubborn, know-it-all newcomer, the man does not take the advice of more experienced travelers and makes the journey alone except for the company of a dog.  It is so desolate and cold, that the man and the dog appear lost before they begin.

The author builds suspense, first, through the setting, the Yukon territory is frigid, cold, cold, cold, 50 below Fahrenheit kind of cold.  This creates an edgy feeling for the reader, it is a wonder how anyone can breathe in weather that cold, let alone make a journey and expect to survive.  Being lost in this wasteland of snow and ice is similar to being lost at sea, the man is drowning in snow and ice. There is danger everywhere, even though he can't see it, pitfalls are everywhere.

" He knew that the coldest snaps never froze these springs, and he knew likewise their danger. They were traps. They hid pools of water under the snow that might be three inches deep, or three feet." (London)

So suspense is built through the reader wondering if the man and the dog will make it to the camp. The story is very repetitious regarding the cold, which acts as the antagonist in this story.

The author uses the third person narrator to build suspense by repeating the warning of the old-timer.

"The old-timer’s advice against traveling alone is frequently repeated, adding a sense of foreboding to the story. Even more ominous is the use of the phrase ‘‘it happened’’ to introduce the two disasters— first when the man breaks through the ice, and next when his fire is extinguished."

The man's lack of willingness to listen to reason from the old-timer and the dog's behavior, he does not like the man, indicate that the man is heading for a serious fall in this story.

The stupidity of the man is highlighted by the author, who allows the narrator to express the dog's thoughts, the dog is smarter than the man.