I substitute high-fiber vegetables (like broccoli, asparagus, cauliflower) instead of pasta in dishes, and have just veggies with the sauce. It fills me up for way less calories, gives me more fiber in my diet, and I still get to enjoy the sauce.
Most surprising, though it shouldn't have been, was education. A complicated insulin diagnosis led me to research my condition at the library and online, and I ended up being interested in how our bodies really function. I discovered effective exercise techniques, why I felt addicted to fast food, and the best diet for my body—good carbs like milk, yogurt, beans and apples. All this information made me see the bigger picture—how my body works, how best to feed it, to make it work correctly and maintain it.
I try to only buy groceries on the outer sides of the supermarket. I learned this in a foods and nutrition class I took in high school and it really works. All your produce, fresh meats, dairy, etc. are pretty much always around the outside of store. I only go into the middle for what I absolutely need—never the frozen box dinners!