I've been on the receiving end of a few "WTF??? Don't you know how to pack stuff???" packages from friends. Besides whatever cushioning or padding you put in the box, once it's all sealed up, shake it gently. If anything's moving around, repack.
About 6-7 years ago, a buddy of mine was going to the Tucson Gem Show and asked if I wanted anything. I asked for some Chinese fluorite crystals. They're octahedral and are usually purple, green or white, and they're about the size of a die (as in the singular of "dice") and they're sold by the kilo. He got me about five kilos in three sealed/taped up bags (each roughly the size of a grapefruit). He also got me an emerald in a small box about 1" square. The fluorite cost about $60 and the emerald was about $200. He put everything in a cardboard box that was at least 50% larger than the volume of the contents. He also wrapped a single piece of bubble wrap around each of the 1-2kg bags of rocks and taped them each with a single piece of cellophane tape. So the bubblewrap was entirely inadequate even if the tape had held. The three heavy bags of rocks were banging around inside the cardboard box during the cross-country shipment. The box looked like it had been used as a football, with big holes torn in the sides. Much bigger than the emerald's box. Fortunately, everything was intact. But I was PISSED. If I had been doing it, I would have wrapped each bag with several layers of large bubble bubblewrap, as well as lined the box with the stuff, and wrapped the emerald's box in with one of the bags. And then stuffed enough bubble wrap in and around the three packages so that nothing could move.
2-3 years ago another friend in LA shipped me her old Macbook Pro. Again, a single piece of bubblewrap was wrapped around the laptop, which was then put in a box that was too big. The computer's case was dented.