for me, I discovered I eat snacks for three reasons:
when I felt anxious/stressed, I snacked to distract myself from the feeling and to "make myself feel better" (which didn't work, I just felt bad for snacking after). So I found better anxiety management methods.
out of habit. I was used to grabbing snacks every time I went to the grocery store, when I passed one particular corner store etc. This was the easiest habit to interrupt because it wasn't actually craving, just a force of habit. A couple of seconds of "no, not this time" until I passed the store or paid the cashier wasn't too difficult and the moment passed as soon as I was out of the situation
because I was hungry. I used to eat lunch and then nothing until dinner so I often times ate snacks in the afternoon because I was getting hungry. I added a healthy snack for the afternoon to bridge the gap between the two meals.
So i'd say figure out why you are snacking and try to figure out a replacement behaviour to fill the role that snacks currently have. Easier said than done of course.
Also I've liked the "imagine yourself as" technique. So you imagine the type of person you want to be, what that person does, what she is like, what it feels like to be her. Then you just keep asking yourself, "would the type of person I want to be do this?". Like "would a healthy person do this?"