When I really want to snack, I ask myself to wait 10 more minutes. If I still want it, I can have it. But then I ask myself, can I wait 10 more minutes? It becomes a game/test. I did it recently on a 3 hour drive and kept doing 10 more, just 10 more, until I made it home.
Lots of fast food companies now have nutrition guides on line. Before leaving the office to get lunch, I pick and choose what I should eat, and then order already knowing how many calories it will be. Removes the guess work and helps me make good choices.