I'm all about free stuff. Free shipping, free coupons, free meals. The meals are the ones I like most. And I don't mind eating other people's food if I know it's good. That being said, I have my rules.
My first rule is that I don't eat out of the trash. No matter how short a time food has been in the garbage or how well I know the original owner or how delicious the still-wrapped half-eaten cookie looks, I stop myself before reaching into the trash. I'm not sure if this rule exists because of my desire to avoid germs or my desire to avoid being caught. I refrain most likely because I don't want to be known as "The Forager" at the office... or at home... or at the city park.
My second rule is that I do not take food left over from others unless I know exactly how long it's been sitting out and I can trace its origins. For example, catered food that I can see being brought out of a just-finished lunch meeting... yes. Homemade meatloaf that I find at 4:59pm outside a dark conference room... no.
The last rule is the simplest. If it's traceable, edible, and free... I eat it. I can't pass up free stuff. And if it's a free meal (an older brother is paying, the company is catering, someone doesn't want the rest of their filet-o-fish) then I'm definitely in.
I even started walking the floors of my building at work to find fresh leftovers or catered wares. I would just walk each floor and find the break room. If I walked fast enough and only glanced, then it didn't look like I was poaching. But I put a stop to it recently. There's a very strange, very sinister-looking older gentleman who I ran into doing the same thing on numerous floors. Once he realized I was co-poaching his territory, he quickened his pace and leered at me through shifty eyes. He scares me enough for me to stop. So now I just ask people in the lunch room if they're going to finish their meals. It's just awkward because I ask as soon as they sit down.