I too have to say, they wrapped and laid in the box deal is horrible for me. I no longer will buy from people unless they use cartons due to that. I never got more than a 10% hatch from any of them that way, and usually had tons of broken ones in the box due to them clanking around.
I use the carton method myself too
wrap each egg in bubble wrap
place big end up in the carton, (very important, air cells rupturing are the biggest problem in shipping, standing them upright helps tremendously, that's the biggest problem with laying them in a pile)
now file the carton tight with paper or any kind of filler and tape shut
file the box half full of packing material, paper, peanuts, what ever, it all works.
center the carton in the box, I use newspaper now to pack around the box so it can not move. Peanuts here can settle and the carton can move to the sides of the box and get damaged.
now finish packing the box full, and very tight, so much so that you can just close it.
tape shut and label the outside, important too. I know a lot of folks say not too, but your odds are better with  FRAGILE LIVE HATCHING EGGS on the outside, otherwise, they go threw the ringer for sure.
the USPS website will send you any kind of boxes you want for free, just go on there and order what you want.
for packing supplies, stay way from the USP store, you'll go broke. If you know folks with a business, they get tons of packages usually filled with peanuts , paper etc, ask them to save it for you. If you know someone with a newspaper route, ask them to save their extra daily papers for you (my brother and brother in law both do, so I'm set on newspaper)
if you can do that, you will have virtually nothing in packing materials.
same with egg cartons, ask your friends to save theirs.
If you ship a lot like I do (30 dozen or so a week) then that will never help, but you can order them from places like eggcartons.com or 
ebay. I get them  in boxes of 100 for like $30, so basically 30 cent each, pretty cheap in the long run.
There are various other ways people swear by, but this works for me both on shipping and happy customers, and me receiving and being happy with the results.
Like others, I based mine off receiving and what I had good luck with. To each his own, and remember that will always be damage. I dont care how you do it, shipping will on average get a minimum of 50% of them. Some times you get lucky and get 90% hatch, but those are the "YOU GOT LUCKY" moments, so be sure everyone you ship to understands this up front and you should have little to no issues.
The more stable, and secure you can pack them, and big end upright (cant stress that enough)  the better results you get. All boxes are going to vibrate like crazy  in shipping, and ones laid on the sides allow all the weight of the internal egg to move from side to side, this is what ruptures the air cells, Big end up placement, still gets vibrated, but the side to side motion is limited due to a shorter distance between shell walls, also it put virtually no pressure on the air cell to rupture it.
God knows it still happens, but much less frequently. If you can get them there without a damaged air cell, then the customer has a much better shot at a successful hatch and repeat business.