I'm always scrupulously honest in claiming things when I pass through customs, whether I'm on vacation or working an international flight. My job depends on it.
During my time out of the country, I keep a little notebook listing of what I'm buying to take home with me, along with the cost. I keep track of things that are exempt, or make a note if I need to check on that further.
I keep informed about what can and cannot be brought back into the country, and avoid buying things that I know will be a problem. It's not worth the risk of trying to "get something in."
When it comes time for me to fill out my customs declaration it's easy. I list the dollar amount that I'm claiming, present the form along with my passport to officials, and I breeze on through. Occasionally I'll get a random question or two. Usually it's something along the lines that I'm not spending enough money on my layovers, which is always accompanied by a hearty laugh from the officials. It's all very quick, organized and efficient.
I can't understand why people are willing to take the risk of not declaring something -- which is actually smuggling. I'm not willing to take the risk of being detained in customs or having my property confiscated, let alone facing the possibility of a stiff fine or arrest and criminal proceedings.
So I ask myself, what was this woman thinking bringing a human head (with teeth, hair and skin) into the US? She was arrested and charged with smuggling a human head without proper documentation, among other charges. (Which raises another question -- What is the proper documentation for bringing in a human head?)