US Photographers going overseas should be aware that departing and entry into the grand ole USofA are not always the same thing. Actually, leaving is not hard at all, but re-entry can be a pain if not planned for properly.
The biggest tip I seem to see is to simply prepare your self for overseas travel; nothing better than planning ahead. Start with our (US ) own customs. They have a website full of info and a checklist to assist you in planning for your travels. The checklist is at the CBP.gov web site.
To (hopefully) keep you from being taxed on your equipment when you re-enter the US you need to complete a CB form 4457. You can get a PDF copy by clicking here. My understanding is that this form must be completed prior to your departure from the US .
The last bit of advice: try not to argue with the customs agent. I am sure they do not like travelers quoting regulations and such. Like a policeman told me one time, “you may win in court, but right now I am the law and what I say goes”. However, by no means degrade yourself or let your equipment be taken from you.