This is a recent discover and it's working well, so I thought I'd share it.
A while back I was visiting family, sitting in the kitchen chatting while dinner was being prepared. Some cut-up veggies were placed on the table within my reach, and I mindlessly scarfed them all down while chatting. I didn't particularly want them, they were just there within reach, so I ate them all.
So I decided I need to channel that into my everyday life. I already buy pre-made salads, but I don't always end up eating them. So what I decided to do is when I get home, I have to put some salad in a bowl and put a fork in it. (I am permitted, but not required, to add dressing, and any salad-appropriate ingredients I fancy.) I then put the bowl by my computer. I'm not allowed to turn on the computer unless there's a salad sitting by it.
I don't have to eat the salad. I can start preparing whatever I'm craving or go straight for the chips. But it's there, within reach, while I stare at the screen. So I end up eating it mindlessly, which fills up my tummy and leaves less room for less healthy food.