Start by finding healthy snacks you like. I still eat chips, fries, etc., but these days, I eat more raw carrots & celery sticks. (But you'd be surprised how few eateries will serve you those...)
I also make my own trail mixes, which contain only nuts & dried fruit. You DO have to be careful with toes, though. You can't eat those until you're feeling physically full. They're too calorie dense to do that. Instead, you nibble on portion controlled amounts (I keep a tiny scoop in my containers), and let the nutrients take down your appetite.
Some recent studies out of the UK also indicated that thick, "creamy" textured meals also have a suppressive effect on appetite.
But the biggest trick is to avoid unconscious eating. You know, just mindlessly snacking away on something until it's gone or you leave the area? I watched an athlete buddy turn down sharing a whole basket of fresh French fries my roomie and I were given when the student union grill shut down for the evening after we got our orders. We then watched as he proceeded to eat at least half of them...without realizing he was eating at all.
A previous year's roomie used to buy jumbo-bags of double-stuff Oreos, and eat them while writing his papers. I watched him down about 1.5lbs of Oreos over the course of about 2 hours while working on one. He made me take the rest away since he still had a lot of work to do and I was on my way to someone else's room.
For me, I broke out of that by telling my friends I was trying to control the number of meals & snacks I was eating. After just a few months of my buddies reminding me of this snack or that meal, I had broken the cycle. That was 1987-88, and I haven't done much unconscious eating since then.
