This used to be one of my big problems, so I want you to know that you are not alone in this AND that you can change your habits. For me, I had two teenage boys, so there was always food going in the evenings. At first, I changed the food. When the bag of chips got opened up, I would go into the kitchen and slice up an apple, in very thin slices to mimic the chips. I remember even using Romaine lettuce, litely sprinkled with sea salt to try and replace the crunchy salty snack.
Then, I also started to change my evening activities. No longer do I sit on the couch for hours at a time (where mindless eating can really take hold). I do more different things now in the evenings - hobbies, puzzles, SparkPeople, walking. I really used to be a couch potato, and could recite any sitcom funny line!
Here is a great article that really helped me: www.sparkpeople.com/resource/nutrition_art
I hope it helps you too.