The Crafting skill can be started in either Neitiznot South or Catherby fishing shop. You simply buy a Sapphire, chisel and Gold Bar. Craft the Sapphire and use it on the gold bar.
Do this for each gem, moving up until you get to Dragonstone. Crafting Dragonstone and using it on a gold bar will give you an Amulet of Glory. You can sell these for an incredible profit. (advised)
This has been a simple and efficient Crafting guide by your friendly neighbourhood skiller,