re bike boxes from a bike store
often a friendly bike store will have no problem unboxing a bike that they need to assemble anyway, so if you are at the right place at right time , and are friendly, you can see them take bike out of box.
Take a photo of how front wheel is ziptied to the frame, and how handlebars are placed etc etc.
you can also ask for all the plastic protection do-dads , they just get thrown out anyway, but seeing how these do-dads are placed and used is a great help to a new bike boxer if you have never done it.
I also have had to return and get a bigger box, as the one I thought would work was juuuuuuust too small.
So as wisely stated by Tourist above, do all this stuff well in advance, and be prepared to spend a few hours figuring out how to do it, making mistakes, having to take bike back out and mucking around with different ways.
Basically though, follow the general layout done by bike manufacturers boxing their brand new bikes, they have it figured out the best way,
zip ties zip ties and zip ties
foam bits and most importantly, those few plastic bits--totally worth holding onto for your return trip--rd protector, fork insert thing, disk brake protector round thing
some zip ties are reuseable, very handy, they have a little depressable release thing to open them.
and of course, tape.
oh, i always reinforce with tape the "grab here" openings on side of bike box, or they can rip easily. Also reinforce the bottom and corners, less damage from dragging on pavement, especially if you plan to reuse the same box on return flight, it will hold up a lot better, especially if any rain is an issue on tarmac, sitting in a puddle or whatever.
it is all doable though