Kirsten Berg, over at the Powell's Books Blog recently posted on the Care and Feeding of Your Books and included this stirring "visible" photo of "A Nicely Packed Box" of books.
Delicious. This is my new desktop background.
Even as a green, untrained youth, I always packed boxes like this. I came to books from a very OCD, comic-book collector's mentality so I have my once near-complete collection of the appearances of Dr. Doom to thank for my formidable packing chops.
UPDATE: A reader asked that I explain why this is proper way to box books. This is a bit like explaining how to breathe for me but I'll give it a try.
The horizontal stacking distributes the pressure evenly. It keeps the boards flat and prevents/cures warping.
The vertical books in between fill the void space in the box which minimizes shifting and prevents the corners and page edges of the horizontal books from bumping together. The vertical books should always go on end (as if on a bookshelf). If you place them open-side down, eventually the weight of the text block will weaken the hinges and binding.
The vertical books should never extend higher than the horizontal stacks, otherwise the box you place on top will mash them.
Always fill your boxes to the top edge (but not beyond) otherwise the boxes will compress and split when stacked. If you don't have enough books to fill your last box, mark on the outside that it should go on top.
If you any have large, folio volumes keep them together. Mixing them into boxes with average size books can apply uneven pressure and deform the larger books
Seal your boxes with tape and try to avoid the "criss-cross" method (which has caused me to destroy a delicate paperback or two).
If you have to stack books in a damp/musty environment for any length of time:
B) keep them off the floor/ground on a table or palette
C) Add desiccant packets
D) Get them back into a humidity controlled environment ASAP
Lastly (and this isn't pictured) if you have numerous mass market or trade paperbacks of the identical trim size, alternate the direction of the books in your stacks (ex: five facing one way, five the opposite, etc). The spine edge is slightly thicker in paperbacks, alternating corrects for this and make for more even stacks (and healthier books).