Crafting an item requires a successful Skill Check with a tool appropriate for crafting an item. You will need all of your ingredients, and applicable tools, implements, etc. This check determines whether or not you successfully make the item at all, and the DC is decided by your GM based on circumstance - Are things easier or harder than normal in this circumstance? Are there other things at play, such as better equipment letting you do the crafting with greater ease?
A typical DC for a moderate or mundane craft would be a DC of 10-12. The higher, the more difficult. Consider that players can get bonuses for skill checks from their class, their spent skill points, and from increasing their attributes. Does failing consume the materials or not? This is usually determined on a case by case basis.
When you craft an item with materials that would allow it to become High Quality Equipment, an additional tool skill check is made to determine the Quality of the item.
If you critically fail this check, the item is crafted at 1 level of quality lower than what the materials would normally allow.
If you critically succeed, or succeed this check with a total of 26 or higher, the item is crafted at 1 level of quality higher than what the materials would normally allow. The DC of this check can be lowered or increased at your GM’s discretion.