One quick and easy thing that works is just to label foods that no one is to eat. It can be as simple as placing a colored dot on them, or a piece of masking tape. After you have used the needed amount of the food, you can either rip it off, or replace the color of the dot. Of course, you will have to talk with your family and make sure they understand the rules. The second part of organization in the refrigerator is your leftovers.
Some leftovers are fair game for lunch.
Others you plan on using for another meal. Again, devise your own label system. As your children get older, they will often have schedules where they can't eat with the family, and have to grab what they can, when they can. In this case, I advice putting something near or on the fridge where you can write down what there is leftover for them to eat. You might even approximate the number of servings, and you might list when it was prepared.