There is a very basic rule to the mechanism of losing weight: you need to create a calorie deficit. This is true not for all but for most people. Eat less energy than you expand and you will lose weight. Most people do this by counting things, such as calories, carbs or Weight Watchers points. I know people who have successfully lost and kept off weight using these methods but it's probably fair to say that for most people this is not a sustainable way of living.
Personally I've had some success with calorie counting, too, but I never managed to keep it up for longer than six months. nor to transition away from it without falling back into old eating habits. For me it comes down to finding a method that works with my personality which means my plan needs to be structured but also flexible. It took some trial and error until I arrived at a plan that feels doable and effective.
And that's it. Three simple rules that help me consume less calories.