When returning to the States, you have to clear
immigration (passport control) first. You are required to present your customs declaration card at that time, for verification. What you may not be aware of is that the immigration officer will often make a mark on the customs declaration card to indicate whether the customs officer should check your bags, or should let you pass without being checked.
While the immigration officer checks your passport, he/she will usually ask some questions about where you've traveled, purpose, how long you've been away, why, etc.
Your answers and how you say them will often decide which mark you get on your customs card.
After years of going through this in international travel, I have come to never be checked at US customs*. Your answers should be matter-of-fact, but casual. Feel free to tell the officer how you enjoyed travelling, but a line about how nice it is to be back home says to the officer that you're a true American. It's not foolproof, but obviously any hesitation or seemingly dodgy answers and you'll probably be asked to do a customs check.
* (The only time I was "checked" recently was when a customs officer was racially profiling passengers by making all, and
only, the minority non-caucasians pass through customs check. But his superior quickly noticed this and he was dismissed from his post, and the subsequent officer allowed me to pass unchecked.)
To borrow a line:
Rusty said:
You look down, they know you're lying and up, they know you don't know the truth. Don't use seven words when four will do. Don't shift your weight, look always at your mark but don't stare, be specific but not memorable, be funny but don't make him laugh. He's got to like you then forget you the moment you've left his side.
If you must carry hardcopy goods, you can always use a little creativity. Customs officers are trained to look for very specific prohibited-but-commonly-carried items, like fruits, grains, drugs, suspicious/uncommon electronics, and so on. If you buy DVDs, get rid of the DVD case and put the disc in a regular CD (you can buy an audio CD, and some of those flip-out dual-disc cases). Hide the DVD covers in between pages of a nondescript magazine. Pack your bags in such a way that photobooks and magazines can quickly be identified as the print material they are, and that other items in your bag can be searched without having to remove the books. To the customs officer, you're just like anyone else bringing home some books and CDs.
Keep in mind, airport security is still allowed to open your bag and check its contents for hazardous/prohibited materials
before you get on the plane. But you will usually just find a TSA "Your bag was searched and we found nothing" note inside your bag.
In the end, however, I agree with
RollyCo, if the risk is too great then you really should just take precautions ahead of time. Encryption is free, disk storage is cheap, there's no reason not to be taking advantage of the technology.