How to craft
Unlike other games, crafting in Guild Wars is not performed by the players. All crafting is done through NPCs. Crafters can be found in every town, and some outposts, throughout Tyria. A crafter specializes in one of three areas: armor crafting, weapon crafting, or rare material crafting. The first two types of crafters are only found in cities and outposts, with a couple exceptions (Sol Pyrrhus, Eternal Forgemaster). Rare material crafters, known as artisans, are only found in explorable areas.
Crafters charge for their services and they don't keep supplies on hand. When you want something crafted you must give the crafter all the material necessary for the crafting and the amount of gold requested to perform the service. For example, Banoit in Ascalon will charge 50 gold, and requires 3 Iron Ingots, to craft a Ringmail Hauberk.
For further information about crafting, see these articles: