Over 10+ years in the jewellery industry there is a few things I've learned about body piercing and I'm going to share a few tips in hopes that you don't end up like one of the horror stories I've seen throughout my career.
Don't Pierce Infants!
Culturally this was done so that female infants could be identified from male infants. (ears and nose) Socially this saves the parent from correcting people who mistake the gender of the infant.
The idea that it somehow saves the infant from pain is illogical - nerves and skin are far more sensitive than an adults, hence why soap is milder and infection risks are higher. Also the body and head have not stopped growing and the alignment of the holes Will change as the child grows - this could mean unbalanced earrings.
Logic aside - the moral issue is forcing a tiny non-verbal human to be physically modified for strictly cosmetic reasons without consent - soo Wait until the child Requests to be pierced.
Gun vs. Professional
A piercing gun loads a blunt earring and a plastic splash guard onto a reusable (!) plastic speed gun. The earring punches through the lobe when it hits the plastic splash guard - i like the analogy of stabbing someone with a spoon really fast!
A professional piercer (preferably certified*) has been trained to align the holes on your ear lobes so the earrings face the same direction at about the same height (ears are not symmetrical on your head). They will use a sharp needle, which is either single use or has been sterilized in a autoclave (in order to keep the shop open they need to maintain the same level of sterilization as a medical facility does when they clean their surgical tools).
*IF* something is maligned with either piercing there is significantly less healing time for the needle pierced hole than the gun pierced hole (remember the spoon)
"I know I'll use a safety pin and a cork! Thats what grandma did!"
Grandma may also have lived in a house with lead paint and asbestos...rest her soul.
I'm no-less guilty of thinking this would be a good idea as a pre-teen, lucky for me my mom caught me before infection set in and i took the earring out of my hand.
The absolute worst memory i have of home piercings gone wrong was a mother and her 3 daughters aged 8-16. All 4 of them had red sore looking noses with earring hoops in them. I asked who did the piercings - mom did, with a safety pin and cork...she sterilized with a lighter after each girl. She pointed to her middle daughter saying that her nose really hurt still. Upon closer inspection of the girls face i could see the thick red/purple spider veins emanating from the piercing hole
"I work in a jewellery store. I'm not a Dr - you need to get her to a Dr right away. And don't take out the earring - it might make it worse!" I said to her.
14Kt gold or higher is your best bet for avoiding infections- 14Kt is 1/2 gold and 1/2 alloy. Silver is also anti-bacterial however some sterling alloys use nickle which approx 10% of the population is allergic to. Stainless steel, titanium and other implant grade metals are also good options. Ceramic, bone, wood and other alternative materials are also available - make sure your piercing is fully healed before experimenting.
Nickel and base metal can be worn at own risk - some people wear them with no problems, others experience itchy reactions and temporary discoloration. Rumors about costume jewellery made with lead, cadmium, chromium, mercury and arsenic are not over exaggerated - it does happen with cheap costume jewellery and it cant be perfectly monitored without testing every piece of jewellery made. There are legal limits in place and all precious metals must be stamped with a purity rating.
Most earrings are pretty straight forward - they are on a post that go through the hole. Heavy earrings may stretch your holes over long periods of time, but this really isnt an issue with modern hollow form earrings.
To stretch your ear-holes - seek professional guidance or risk a keloid.
For nose piercings - one-size does not fit all. Wearing a mass produced nose screw may result in lil pig tail metal booger hanging out your nostril.
Its best to find a goldsmith who either works in a piercing parlor or knows about body jewellery - custom work is best.
In closing - if its your body, do with it what you will.
If you have health concerns regarding any piercing go to your Dr.
If your earring holes have grown in, or you have had an ear or piercing infection within 3 months - do not try on earrings at any jewellery store! Even though jewellery is sterilized after a client tries them on its still unhygienic.
Preferably certified* - Contemporary body piercing techniques have been co-developed by Fakir Musafar who is heralded as the "Father of the Modern Primitive Movement". Those who attend his intensive courses in San Francisco are given a certificate of attendance. In the industry this is the highest level of formal recognition for body piercing and branding.
Apprenticeship under those who have studied his techniques is considered the most sophisticated and skilled in this field.
No such training is required of anyone who uses a piercing gun.
(!) - because a piercing gun is mostly plastic it cannot be put inside an autoclave to be sterilized. An autoclave uses pressure and heat - both of which the plastic piercing gun cannot endure. (see image)
Professional piercing salons require licensing - to maintain their license they must have an impeccable record of cleanliness.
No such licensing is required of anyone who uses a piercing gun.