Bring (a copy of) your original invoices
If you are flying outside the EU, you may have to prove to customs that you already had your camera in your possession before you travelled. You do this with the original invoices. Bring a copy of these with you (leave the original safely at home).
The invoices for your purchases at Photospecialist can easily be found and downloaded in your account.
Keep your photos close at all times
This is more of a tip for during the return flight, but just as important. By the end of your trip, you'll probably have taken hundreds of great photos. It would therefore be a shame if you lost all these memories because (despite all these tips) something happens to your belongings on the plane. Therefore, keep your memory cards (and possibly a hard drive) in your jacket pocket. It couldn't be closer.
Better yet, keep your tickets all in a card case which you then put back in your pocket. This way you won't have any cards lying around.