The hood piercing is often mistakenly called a clit piercing. The hood piercing actually passes through the clitoral hood, whereas a clit piercing goes through — you guessed it — the clitoris. Sometimes a triangle piercing will be mistaken for either a hood or a clit piercing.
Hood piercings are done either vertically or horizontally:
A vertical piercing is made at the top of the hood, exiting underneath the hood and above the clitoris. Either a barbell or a captive bead ring can be worn, but a curved barbell fits the natural shape of the hood better and the bottom ball rests on top of the clitoris. This orientation is usually gotten when the piercee is looking to increase sensations. As with all female genital piercings, a certain anatomy is required to have this piercing: the hood must be long enough and have enough room under it to accomodate the jewelry.
A horizontal piercing is made about ½–1 cm above the edge of the hood. Either a barbell or a CBR can be worn in the piercing, but CBRs are very popular because the bead of the ring usually rests on top of the clitoris. Horizontal piercings are generally better for women with especially sensitive clitorides, since the jewelry isn't often in direct contact with the clitoris.
Both orientations are usually pierced with a 14–10g CBR, since a ring is much easier to clean than a barbell. After the piercing is fully healed, some women choose to stretch the piercing to slightly larger sizes, which will often increase stimulation.
The piercing does hurt, but not as much as a clit piercing hurts. The pain is generally over is about three seconds, and is usually followed by only a little soreness or throbbing if the procedure was done correctly. It doesn't bleed much normally, most women report only a few drops of blood if anything.
Healing period is around eight to ten weeks. Sex of any kind must be avoided until about three weeks after the piercing (including masturbation), and bacteria hangouts (dirty hands, swimming pools, etc.) are to be avoided until the piercing is fully healed.
After an extended period of time, some women report feeling less sensitive to the piercing as they had been just after getting it. This is because the area has become accustomed to the jewelry, not because the clitoris has decreased sensitivity — changing the jewelry or leaving it out for a few days will restore the sensations.
No personal experience in this one — quotes and women's opinions paraphrased from BME's collection of piercing experiences.