1. Keep a box with all the styrofoam, wrapping material, small boxes and bubble envelopes you get from packages that you can use again. It will come in handy!
2. Find a box that fits your shipment, and if you can, choose one that fits through a mailbox slot. This will make shipping cheaper, because it will be considered a letter and not a package!
3. When shipping overseas, keep customs into account. If you're shipping just a few minis, label the package as a "gift". Customs vary in each country, so do a little research to see if and how you need to declare the contents of your package.
4. Use styrofoam (see image) so your minis won't get shuffled around. Pack them snugly, and if you can, use some covering material as shown. If you can shake your package after packing, and you hear nothing shuffling around, you're good to go.
5. Get a bubble envelope or a sturdy box, and close it well with tape.