[2020] How do i increase my item´s level?

Originally posted by seven: You put points in Archery under the Agility skill.

To elaborate, crafting quality is tied to the skill that bolsters the items effects. EG: to raise bow and crossbow crafting quality, you raise the archery skill in agility. Or for clubs you raise the club skill in strength. Or for tools like the pickaxe you raise the miner 69er skill in strength, and so on.