Honestly, the only thing I've found that helps with between-meal snacking is 100 percent will power and resisting the urge to eat. And this is very hard.
Protein does fill you up a bit better than other things - I know when I used to eat omelets in the morning, I'd stay full for quite a while. Maybe try a fruit smoothie - these would be good as either a meal or a snack because they're so filling. To make one, mix 1/2 cup vanilla yogurt, 1/2 cup of whatever fruit you want (I use frozen berries), a drizzle each of milk and any fruit juice you have on hand. Mix in a blender, and if you like, strain out seeds, pulp and skin with one of those mini hand strainers (the kind used to pat powdered sugar onto cakes). This makes a very big glass and it's very filling...and healthy.
Also, try doing some light exercise to ward off hunger. If you want to snack, find a spot and do a couple crunches, a couple squats, and maybe a push-up or two. Nothing strenuous.
Yeah, I should take my own advice.