1. I buy new heavy duty boxes from a local box supplier company. (24 X 24 X 10, works for most receivers, amps, TT's , etc) I've found that a lower profile box will survive better, than a box, that is the same dimension on all sides)
2. I wrap the unit in large (1" min) bubble wrap. I put 4 layers on front face and back face. (I don't use anything smaller than 1" bubbles) Then another layer of bubble wrap goes all the way around, holding the extra layers on faces All the bubble wrap is wrapped with some packing tape to stay in place.
3. I line the box (all six sides) with 1 1/2" white rigid insulation board.
4. Any extra space between the unit, and the 1 1/2" liner, is filled more rigid insulation board. (I usually use 1/2" board for this)
5. After the unit is pretty tight with insul board, I fill any small voids with peanuts.
6. The final layer of 1 1/2" insul board goes over the top of everything.
7. Double layers of packing tape over box joints.

It makes the unit inside the box tight, and can't move. Makes the walls of the box very stiff. Nothing will come out even if the outer box gets cut/split.

From Dave:

I almost never buy packing materials, almost always recycling something. I do use used boxes but I don't skimp on the packing job, and I know when a box is too worn out to be reused for shipping.

I start with one box somewhat larger than the unit I'm shipping (the heavier the unit the larger the box). I put several layers of "padding", some type of cushiony (but firm) type material in the bottom, sometimes several layers of crumbled up balls of newspaper, sometimes layers of carpet padding, crumbled up plastic grocery store bags (lots of them), you name it, I've used it all. The important thing is having enough padding so that it acts like a shock absorber and the unit just "floats".

After I have layers of padding on the bottom I put the unit in, then I add padding all around the unit, using special care for the faceplate (bubble wrap etc) and special care around knobs, switches, speaker terminals, fuse folders, antennas, or anything sticking out that could break. I use small Styrofoam blocks around speaker terminals and such so that nothing is actually touching the speaker terminals, the Styrofoam blocks just touch the back of the unit. Same thing to protect glass faceplates etc... each unit is different and may require different methods.

After I have all the padding around the sides I add layers of padding on the top. One thing to keep in mind is packing peanuts, these should only be used as a filler to "fill in" holes, never just fill a box with these and throw a unit in it. When I'm done with that box, I start the whole process over with a larger size box, put padding on the bottom, put first box that I just packed in, then add padding to the sides and top, I probably use peanuts more here than anywhere, between the two boxes but I still make sure the box in the center is secure and won't "shift" by using some pieces of padding. Add padding to the top and tape shut.

From Grumpy:

Almost all of my boxes come from a local box company. I just buy em new in qty 10-20's depending on size. Heres a tip for you guys if you didnt know.

If you shop for boxes ask if they have any preprinted boxes that a customer didn't take. That's how I got my 8x8 cubed boxes dirt cheap. An old customer of theirs didnt like the printing so the box company was stuck with them. After they have sat on them for a while they are willing to wheel and deal by then.

I have revised the way I ship larger items like a Pioneer SX-1050s. I now bubble wrap usually 6 layers at least. Then I hand make a box from sheets of 48" X 48 " single wall cardboard. I make the box very tight around the Receiver. Then I use sheets of 1" foam insulation to encase the the handmade box. From there, I use a 200 pound double walled box that the inner box fits in with at least 2 inches all the way around. Then I fill in the gaps with more sheets of insulation.