For me, I consider a binge something that happens when I eat for the sake of eating. For example, I was really craving a huge, ice-cream covered brownie last night. Instead, I had one bite of the homemade brownies I made and part of a sandwich... (which, for me, was much better than HUGE hunk of brownie and ice cream by far.) So, I beat that craving.
The next day, I didn't just give in to my craving. Instead of just having a huge brownie with ice cream, I had that along with cheese dip, frozen pizza pockets, and BBQ chips. I can tell I'm binging by the mess I make..I've gotten to a point where I don't end up binging until I'm completely sick...but I do prepare the amount of food it would take for me to get that way. I also planned to eat chili...(I took a few bites of my cheesy, gooey, Frito-invested chili and threw it down the sink,) the whole rest of the pan of the brownies (by the time I quit picking at them, I prepared a huge chunk with chocolate chips and tons of ice cream...and I also threw over half of it down the sink,) and I also planned to eat the whole thing of cheese dip. I had a few bites.
Excess for the sake of excess is binging for me. I usually end up laughing hysterically in the process of my eating...and that's kind of a telling sign that something is up.

The moment eating becomes this huge, emotional, mental mess....I know that I'm setting myself up for a binge.