He uses his ninja skills, of course. His shadow clone jutsu can be very useful for scouting and distraction. And his Rasengan is a powerful attack that can fend off many threats.
Naruto might survive by making friends with the local animals. They could warn him of approaching danger or even help him fight off enemies. Also, he could find sources of food and water in the forest, like a hidden spring or edible plants.
In fanfiction, Naruto could survive in the Forest of Death by learning the ways of the forest from the spirits or ancient guardians that are said to exist there. He may gain new powers or knowledge that allow him to adapt to the harsh environment. For instance, he could learn how to camouflage himself like the forest animals or use the natural energy of the forest to heal his wounds.