Because of dimensional penalties, it's often less expensive to pack in two smaller cartons, One for the frame, one for the wheels (with skewers removed). Go the sites for the various carriers, ie. Fedex Ground, UPS, USPS and read the rules on size and weight and work within or around them o save dough.

The most important thing to do whenever you pack a frame or bike, is to put pacer blocks in the fork and rear dropouts. Properly braced these are strong and travel well. Not braced they're prone to crushing. You can make a brace with a piece of 2x1 and 2 nails, or get one free at any bike shop (fronts are much more common than rears).

Also, I find it advantageous to remove the RD (leave the cable attached) and tie it inside the rear triangle for safekeeping. Also, shove a cork of some kind in to the top of the seat tube to prevent damage there, especially if it sticks out above the top tube. If you have a threadless headset, you can save space, and the fork will be safer if you remove it, but this usually isn't worth it for threaded headsets.

The rest is about properly padding the frame tubes to prevent cosmetic damage, and securing removed parts **** pedals so they don't move around and cause damage. Be sure to pack small parts in zip-lok baggies, and/or in a small box within the box so they don't get lost.