How to find out where the Fang and Bone is?

The Fang and Bone appears outside every major settlement between 9pm and 5am (except Goron City) in the same spot every night.

It's fairly easy to locate, simply by finding a vantage point and scanning the surrounding area.

The exact locations of the Fang and Bone are as follows:

• underneath the bridge to Tarrey Town in Lake Akkala in the Akkala Highlands
• west of the Ancient Furnace in Hateno Village in East Necluda, on Korne Beach in East Necluda
• among some ruins west of Gerudo Town in the West Barrens in the Gerudo Desert
• south of the Hebra Trailhead Lodge in the Hebra Mountains
• southeast of the Veiled Falls in the Lanayru Great Spring
• above Lantern Lake in West Necluda.

Source

It is important to note that he will only appear when you show up in an area after the time that he is meant to show up. He will not simply materialize in front of you when the clock strikes 2100. Your best bet is to wait until 2130-2200, and approach the area/teleport to the location then, but you can re-teleport to the same spot to re-load the area (I have personally tested this).

Alternatively, people have suggested locating him under the Bridge near Tarrey Town, which seems to "reset" his cycle.