Get a heat pack. I like these ones (available for $1 at J&L Aquatics).
Read the directions on the back of the heat pack. Different brands have different instructions!!!
In this case, this pack heats up as soon as the plastic wrap is removed and the pack is exposed to air. It doesn't need to be shaken or mashed up or anything. This heat pack had red stripes on one side, and the red stripes need to be facing the critters. I
loosely wrap a layer of newspaper around the pack keeping attention which direction the red stripes are, and tape it to the inside of the lid. You can skip the newspaper if you want, but I find sometimes the heat packs fall off the lid if they aren't wrapped in newspaper.
Put the lid on the styro box.
Close the cardboard box, and tape it up real well on all edges. Put the address and phone number on at least two sides, and put LIVE FISH (even if it's coral...a lot of people don't understand "coral" can die) on every side along with a big arrow for the right direction up. I also like to put a note on the top "Please call upon arrival".
Now, maybe you're shipping a few bags...so you are using one of the styrofoam fish boxes.
You can cram as many bags in these as you can fit, but be sure to keep fish bags upright so they have enough room to swim. Any bags that have styrofoam disks need to be upright as well. I like to put a layer of packing peanuts on the bottom to keep the water as well insluated as possible.
Fill any void space with packing peanuts. I ran out of packing peanuts. You need to fill the box
all the way up!
Tape the newspaper wrapped heat pack (or two) to the lid.
Put the lid on the box, and run a ring of packing or duct tape all along where the lid meets the box (I should have got a picture of this). This way if the bags leak, and the box is turned upside down the water won't leak out of the box. Put the styro box into the cardboard box.
Tape 'er up real good, and write what you need to write (as above).
So that's it! Feel free to suggest slight changes if you'd like.
Also, feel free to send me from frags to practise your shipping!!!