When I first began writing one of the first challenges I faced was how to ship my signed paperback copies to my readers. After several variations, I have found what works best for me, and so far have had only happy customers on the receiving end.
This is by no means the only way to ship a book, and there may be a better way out there (leave a comment if you have a better way!), but this is what is working best for me right now.
1) Wrap the book in plastic wrap. Yes, you read that correctly. From what I've gathered, media mail is one of the least carefully handled mail types, so I always wrap my book in plastic wrap just in case the box gets wet. It probably won't save it if it gets dunked in a puddle, but it gives it a little protection at least.
If you start with the face/cover of the book on the flat part of the plastic wrap, it lets the crisp image of your cover shine through. Make sure that you overlap so that no parts of the paper are exposed.
When the book arrives, it will be shiny and new, protected in it's plastic wrap.
Note - only do one layer of plastic wrap, two at the most. Any more than that and it gets really hard to unwrap.
Next I cut a piece of cardboard to match the inner dimensions of the box in which I ship the book. I then wrap a single band of regular tape around the book and the cardboard, securing the book to the center of the cardboard.
This is also where the plastic wrap comes in handy, as running tape around a bare cover might result in the beautiful image being damaged. No good!
Then carefully put your book in. See how the cardboard almost perfectly matches the box interior? This means that even if the box gets jostled, shaken, dropped, or kicked, your book is safely nested away from the edges and should be protected.
Finally I put more packing material on top of the book, and an invoice. Actually, the invoice goes under the packing material so it's a little more protected, but I was distracted while packing this one and so it went on top. It was fixed before shipping though!
I always, always recommend an invoice of some sort. Templates can be found online or through Microsoft programs, or you can just make your own. It's a second way to provide an address, and also let's your customer know what is in the box.
There you have it! Once the box is packed just tape it up, put on a label, and off to the post office you go. If you are just sending a book feel free to use the media mail option, which will safe you a significant chunk of change over time. Just be aware that there are very strict requirements for media mail eligibility, and the post office system does open boxes to inspect!
Last addition - Most of my packing material is actually reused from when I order the books from the printer. I also save all tissue paper from birthdays and Christmas and use that as well. I either reuse the printer's boxes, or just purchase them from a supply store like Staples or Target.