My favorite PC in a long time is an artificer, so ...
Okay, first off, the really, really basic part: Craft Wondrous Items allows you to trade a feat slot for money, XP, and customization.
Anyone, generally speaking, can get a ring of protection. You, however, have spent a feat to be able to get it at half price (plus a bit of XP) when you need it.
Craft Wondrous Items covers, basically, those magic items which are not specifically covered by another feat: gloves, clothing, cloaks, bags, ioun stones, etc.
When you go to craft an item, you first determine its Market Price. You then must spend half of that amount in gold pieces, and 1/25 of that amount in XP, to craft the item, which takes 1 day per 1,000gp of value.
So, crafting a 2,500gp item costs 1,250gp in raw materials, 100xp, and 3 days.
Generally speaking, there are no checks to be made; success is automatic.
When you are making an item out of the DMG (the "stock" items, as it were), the prereqs and costs are easy to find. Note that every item has a CL (Caster Level) entry. This is representative of the most common level at which the item is crafted, but it is
not a hard requirement. Should you wish to make the item at a different CL, this is usually doable, but the cost and effectiveness of the item may need to be adjusted.
For instance, the Pearl of Power is listed with a CL of 17. This means that, should the DM throw a random Pearl of Power into a treasure horde, it will likely have a CL of 17. If you wish to create your own PoP, you can set the CL at any level up to your own CL, so long as you are still able to meet the prereqs. Since the prereq for a level 1 PoP is "Ability to cast 1st-level spells," you could make a CL 1 PoP (1) for 1,000gp.
Other items, like Boots of Levitation, have an effect which is based on their CL. In this case, the boots act like a levitation spell cast by a 3rd-level caster each time they're used (including how long they work before you need to command them again). If you want the boots to last longer, you'll need to increase the CL, which will increase the cost.
When costing items which are not already present in the DMG (including items reliant on their CL at a different CL than is listed), you'll need to use the formulas to estimate the cost.
This is a delicate process, and should always involve your DM. For the most part, magic items have a cost expressed as:
[Constant] * [Variable 1] * [Variable 2]
In many cases, Variable 1 and 2 are the same thing: attack bonuses, save bonuses, etc. In other cases, they're different, spell and caster level being the primary one.
Additionally, when it comes to Wondrous Items, you'll need to be careful about something called "Affinity." Broadly speaking, each magic item slot is designed to do certain things: hands to make you quicker, belts to make you stronger, etc.
If you try to go against the slot's affinity (by making boots that increase your Intelligence, for instance), you pay a penalty of 50%.
Sound good so far?