More often than I expected, airlines and travel companies offer me free stuff because I am a journalist. As a rule, I will not take it. This includes upgrades to first and business class and free flights. Sometimes, it includes hotel rooms, or even use of a cell phone while traveling.
I learned not to take free stuff as an undergraduate at Northwestern University's Medill School of Journalism. It might be a slightly outdated concept, but I don't think journalists should accept free gifts of value from people we cover. Perhaps at some point my opinions will change, especially if the publications I write for can no longer afford to send me to report stories.
For now, I'll take a lunch or an amenity kit or some other kind of small gift, but that's about it.
There is one caveat to my rule. If I am assigned a story by a reputable publication that has different ethics standards, I will follow the publication's standards, rather than my own.