I pack our bikes much the way Tourist in MSN's pictures show.
We have a good supply of packing materials from our LBS: fork spacers, derailleur protectors, Axle protectors, etc. We use pipe insulating foam to protect the frame. The front wheel's quick release skewer is zip tied to the foam on the seat tube; and the pedals are put is a plastic bag, and zip tied to the seat tube inside one of the water bottle cages.
My wife's bike, with a 47 cm frame, my not even require removing the seat to fit in a medium sized box recycled from our LBS. The front fender and rack are taken off. If I do have to take the seat off, I pull it straight out to prevent scratches on the seat post. Even if I could get a good fit pushing the seat down, I don't do it to prevent scratches to the seat post. Mark the seat post height with a piece of tape.
If you are not using canti brakes, use a Problem Solver locking spacer to hold your fork in place, and you don't have to worry about headset adjustment.
This box was on four different flights (4 loadings and 4 unloadings) getting to the start of one of our tours in Europe. It is a little the worse for wear, but the bike was not damaged at all. I've started reinforcing the hand holds on the boxes with duct tape and they don't tear out as easily.
