One of the habits that I've overturned was my mindless eating. These days, every time I eat, I make sure that I'm at a dining table, and that's the only thing I do. I don't eat anymore while reading, watching TV, or watching a movie at a cinema...although I've allowed myself a few indulgences when all the Hollywood summer blockbusters came out.
If any of you still do this habit—notice that it's harder to stop eating, especially when you have a big tub or pack laid out in front of you, and you're enjoying a good show. My old favorite TV snacks were peanut butter M&M's—I could eat half a bag in one go. 500 calories right there, and it's not even mealtime. Yikes.
If you still prefer a TV or movie snack, you could try just taking with you a single portion, to avoid overeating. But for me, personally, I've found that limiting my eating to a proper dining table makes me more focused on what I eat. I end up being satisfied with less, since my mind is solely focused on the act of eating, I am more aware of when I should stop.
One night, after dinner, I had one Ghirardelli milk chocolate and peanut butter square. Not only is it less sweeter than peanut butter M&M's, but I found myself satisfied even with just one square—only 75 calories for dessert. Not bad.