I try and get out of the house. If that doesn't work, I try and find ways to keep distracted. Whether a good book, good conversation, hobby, study, work, whatever.
A real good one if you're doing this mostly at home: Don't buy unhealthy foods or snack foods. If you don't buy it, you won't eat it. If you must have snacks, find healthy alternatives. Yogurt is great for something sweet. Lactose intolerant? Try a tangerine, banana, or even Fiber One granola bars. Want salt? Goldfish, cottage cheese, freshly made popcorn (no butter!) and green pea chips are great.
Also, if snacking, don't take the whole bag. Only take out a handful or little baggie full and put the package away. We eat more of something the bigger the container we eat from (there are studies on this, I bet it would come up on Google).
Another good one: hide the unhealthier things out of site. If you don't see it, you wont eat it. Example: I love me some girl scout cookies (Samoas!). I purposely put them in the depths of my frige so I will only eat one when I specifically think about it, not on a whim.
Hope these help!