This Northrend Skinning leveling guide will show you the fastest way how to level your Northrend Skinning skill up from 1 to 75. Your skinning doesn't determine the number of leathers you get from each mob, you will get the same number of leathers with Northrend Skinning 1 as with 75.
Learning Northrend Skinning
Go to Northrend and learn Northrend Skinning from one of these NPCs below:
Derik Marks at Dalaran. (Northrend, not Legion Dalaran)
The Ruby Sanctum - (level 98+ players)
You have to be at least around level 98 to be able to solo this raid quickly. Check the places mentioned below if you have a lower level character.
The portal to this instance is located underneath the Wyrmrest Temple, in Dragonblight at Northrend. In (Legion) Dalaran you can port directly to Wyrmrest Temple from the portals in the middle.
Raid difficulty doesn't matter, so you can set to normal, but you should always set the Legacy Raid size to 25 man because it has a lot more mobs. Right click on your own portrait and select "Raid Difficulty" to change raid size and difficulty.
You should stop twice to kill and skin the mobs because the corpses might start despawning before you can skin them if you try kill all of them in one pull.
You can reset the instance by right clicking over your own portrait then click the "Reset all instance" button. This restarts the whole instance and all mobs will be back. You will reach Northrend Skinning 75 by clearing the instance twice, which takes around 10 minutes.
There are lots of Rhinos and Dragons here. You can also go into the cave called Gimorak's Den, I marked it with a yellow X on the map.