1) It makes sense to put a few remarks about how the food is prepared (is it broiled chicken or fried?) and the portion size (is it a cup of pasta or five cups?) to get an idea of how much you're eating, calorie-wise after a few days.
2) Make a note of the time you ate the food and whether it was a meal or snack. You might later see that you overeat if you wait to eat breakfast at 10:00 am, but if you eat at 8:00 am it appears to be a smaller amount of food. Or, you might find that if you have a small snack at 4:00 your dinner is much smaller, but if you don't snack you are so hungry at 6:30 that you eat a larger amount of food for dinner.
3) Where were you when you ate each meal or snack (was it in the car? standing at the kitchen sink?) This can give you ideas to reflect about when you see a trend. You might find that you eat a lot more when you dine at a restaurant than you do at home. Or that you want to declare a "No Food Zone" in your living room, at your desk, or somewhere else you find that you do a lot of mindless eating.
4) Sometimes it's helpful too look at why you ate and how you were feeling when you ate, if you tend to be an emotional eater. Were you actually hungry? Or maybe just bored? Were you anxious about something and turning to food to calm yourself down? Maybe it has become a habit to munch on a bag of chips while watching a certain tv show. Consider having a column labeled "how hungry" on a scale of 1-10, or "mood" or "activity".
By having this food log, we will be able to determine or be attentive to the foods that we take. You can view more helpful tips here: online exercise videos