A piercing through the nipple. Can be horizontal, vertical, diagonal, slantways, etc. Applicable to men and women. There can be multiple piercings in the area, though 3 per nipple seems to be the limit.

Jewelry to begin with is usually a CBR (Captured Ball/Bead Ring), but later can be changed to curved bars, straight bars, shields, etc. Mine were done with 14 gauge CBR's, but they grew out. When I get them pierced again, I'll have the guy up the size, because bigger gauges migrate less.

Aftercare list from Stainless Studios. Stolen from BME:

Wash your hands before touching your piercing.
Wash the area surrounding and including the piercing with an antibacterial soap at most 2 times a day.
Concentrate on the piercing itself and soak away the crust (do not pick or pull at the crust -- just like a scab, it is connected to the healing tissue).
Lather up the jewelry and move it back and forth through the piercing six or seven times.
Allow the cleanser to soak in for one minute.
Rinse off the cleanser with some warm water and move the jewelry a couple of times to allow any excess cleanser to be removed from inside the piercing.
Pat dry the piercing – Do not rub with a towel.

If you notice any errors or further recommendations, /msg me, and I'll add them. Or you can too.

I've heard of skadip's methods, and they work. There's more than one way to skin a cat. I've done it my way, and it works. But I've heard from some people that they like it the salt-water way. YMMV