Keep track of everything you eat or drink, especially little nibbles – they soon mount up. Not only will you be able to see which areas can be improved, but you’ll see a pattern to your eating habits.
Obviously it’s not always practical or possible to know exactly what’s in your food, e.g. when dining out, but with a bit of common-sense and a some savvy, you’ll be fine. And if you’re out, don’t wait until you get home to log what you've had, use a Smartphone App – there are plenty to choose from, and a lot of them are free. If you don’t have a Smartphone, use a pen and paper.