Among many well-known and unknown reasons to get flagged, here are a few of the most obvious ones.
Having Passport Stamps from Certain Countries
If you have passport stamps from certain countries (even from a trip you took years ago), you may run into trouble at customs at home or abroad. For example, trying to enter certain Middle Eastern countries with an Israeli passport stamp in your passport can cause trouble—so much so that Israel began a pilot program this year through which visitors get a separate entry card rather than a physical mark on their passport. Likewise, having a stamp in your passport from Cuba will likely raise some eyebrows at the American border.
To this, I would add visas from places that might draw attention. The most obvious: Communist countries, and countries at odds with the U.S., such as Cuba, Venezuela, Cambodia, Vietnam, Afghanistan, Pakistan, Syria, and Iraq.
Wearing Hiking Boots
For nations concerned about biosecurity (specifically, keeping non-endemic species from invading), hiking boots are a big risk, as they could be contaminated with soil, seeds, or water from a hike in another country. If you’re traveling to Australia or New Zealand, for example, you’ll need to declare your hiking boots, and you may have to wait while they are cleaned or even have to throw them away.
This actually happened to us, on our way to New Zealand (South Island) from Australia (Queensland). The same warning also applies to golf shoes.
Not Knowing Where You’re Staying
Planning to be spontaneous and book a last-minute hotel in the U.S. when you land? Forget the exact address of the friend you’re staying with? Prepare for some extra scrutiny from the CBP. The customs declaration form requires that every traveler arriving in the U.S. indicate where he or she will be staying; if you don’t know, CBP agents might deny you entry into the country.
Always have at least one night’s stay pre-planned and pre-paid. I repeat. Always!!!!
Bringing in Food (Even an In-Flight Snack)
Brought a snack on the plane but forgot to eat it, or saved some of your in-flight meal for later? Better declare it or throw it away before you disembark your flight—because failing to declare a food item can result in a minimum $300 fine. This goes beyond fresh food—processed food must be declared too. Odds are you’ll get to keep the prepackaged candy you bought as a souvenir and you’ll have to toss that fresh food. But the important thing is that you declare all food items so that the customs officer can make that call.
I have experienced very few problems with food of any kind. But I have seen other travelers get caught with spices, herbs, and tea. Who knows what those things really are? Meat and meat products always seem to be a problem as well. I think the drug sniffing dogs are just looking for a snack!
On my recent trip to Ecuador and Colombia, I did experience much faster processing than my two traveling companions. Mike, a U.S. citizen, for some reason, had an unreadable chip in his passport. This was a problem everywhere. Barry, from South Africa, well that says it all, South Africans in South America? Some places required a supervisor for him to get through!!!
Some immigration officials like to browse through my passport to see where I have been. I would expect this to be a problem in the future, as I now have a Russian visa in my U.S. passport. I had a guy in Chile or Argentina object to me writing in my passport, that I was allergic to penicillin. The nerve of the guy!
When I see suspicious looking people going through Immigration, I wonder. Do they go by how you look, or how you act? Also, it seems better dressed people have no issues. So, in that regard, always look your best, and keep the torn jeans and Harley tank tops for rock concerts! Oh, and cover your tattoos!