Have my earlobes pierced - twice in one earlobe and once in the other.
Nowhere else. A college friend and I one-time considered belly button piercing, but after doing a quick call of local doctor's offices, I could find no doctor who recommended it. Most said it would be longer healing than I could imagine and it would be difficult to keep clean while it healed.
Which of course then makes me gross out at all the piercings in people's private parts. Even a nose piercing, while traditional in many cultures makes me wonder...does it leak when they blow their noses? And of course, the ability to keep it clean completely depends on the person's diligence, so who knows how many people have stopped worrying about how clean they keep their clitoral piercing or Prince Albert?

Yes, I think cleanliness is certainly key...even in the earlobes. If you leave earrings in too long, gunk, for lack of a better word, will accumulate. It's probably dead skin cells mixed with natural body oils.
Enough of that.
I didn't have any problems whatsoever with my navel piercing. I did get 'high' about ten minutes after leaving the piercing salon with my instructions - so much so that I had to find a seat fast. I guess it was a surge of endorphins (or adrenaline, or something) caused by the shock of the invasion. It suddenly made sense to me about how some people can become 'addicted' to body piercing. I've never felt anything like it before or since.
The waistbands of most of my clothing chafed the area while I was healing, so I wore shirts outside with the pants zipped but unbuttoned with the flaps tucked in for about six months.
By some weird twist of immune system logic, after I had my ankle surgery with surgical stainless steel pins, plate, and screws inserted, I haven't been able to wear surgical stainless steel in the navel. Only platinum...everything else I've tried causes a reaction. No change observed post-surgery with in the earlobes...
I'm glad I had surgery to remove the ankle hardware, but I envision that there is still stainless steel residue there causing problems...my left ankle retains fluid and is perpetually swollen compared to the healthy one.