One good example of textual foreshadowing comes early on:
He plunged in among the big spruce trees. The trail was faint. A foot of snow had fallen since the last sled had passed over, and he was glad he was without a sled, traveling light. In fact, he carried nothing but the lunch wrapped in the handkerchief. He was surprised, however, at the cold.
(London, "To Build a Fire," eNotes eText)
Referring to the trail as "faint" shows that the area has not been traveled much recently; others know how dangerous the cold can be. The man's lack of a sled, and his only item being his lunch, shows the lack of preparation that leads to his death; he is not mentally prepared for the extreme cold of the Yukon and so does not bring enough matches, or a flint-and-steel which cannot burn out. Finally, his "surprise" at just how cold it is shows his ego and his failure to prepare; if he had listened to the advice of the Old-Timer, or simply used more common sense in preparing, he might have survived.
Each of these points indicates his later failure; he has no sled, and so only one dog -- he might have been able to snuggle in with multiple sled-dogs and survive that way. He only has his lunch and no other supplies -- he was not thinking ahead. He is surprised at the cold -- because he didn't listen to advice, and so the cold is what kills him.
Well, to begin with, this picturesque mountain setting is described like the gates of Mordor from Lord of the Rings, "It was a clear day, and yet there seemed an intangible pall over the face of things, a subtle gloom that made the day dark..." This pretty well tells us that this guy isn't in for a pleasant journey. The next thing we notice is that it's really damn cold,
"Fifty degrees below zero meant eighty-odd degrees of frost. Such fact impressed him as being cold and uncomfortable, and that was all. It did not lead him to meditate upon his frailty as a creature of temperature, and upon man's frailty in general."
Okay, so he had his long johns on; this is still death cold and not merely travelling cold. This tips the reader off that not only is this guy a "newcomer" but he is smug about what nature can throw at him. Rule #1 in the Yukon is don't give nature any attitude, she'll back slap you every time. She, of course, ends up doing this but I called it in the first paragraph!