Reading food labels is very important when you are trying to lose or maintain your weight. Basically, you need to watch your carbs, fat and protein intake, but there are a few additional things to look out for. Apart from information about macronutrients, there are also details about sugar and sodium in food. This must be taken seriously. Note that sugar can be labeled as maltose, fructose, glucose and sucrose, but it's still sugar.
A product that has a good carbs/fat/protein ratio but contains a high salt content can be damaging to your health. The recommended sodium intake is around 2,300 mg per day, which is equivalent to one teaspoon of salt. Try to choose foods that are low on salt and contain no more than 0.3g of salt per 100g (or 0.1g of sodium per 100g).
Lastly, you need to pay attention to serving size. While nutrition information is usually stated for 100 grams, you may eat more and you'll need to recalculate to find out how many calories you really consumed.