Fedex used to have the best prices.
On expensive bikes/frames sometimes you might want to actually build a box/crate with 2x2" and cheap paneling. You can build a crate to smaller dimensions than a cardboard box, since it is rigid and offers more protection.
Find out what the effective dimensions(or dimensional weight) will be before putting up a shipping price. On bulky things like bikes, you are charged by size not so much by weight.The crate allows smaller dimensions.

Like others said-start small.
Luck
Charlie