Start with the serving size. Many labels show values per 100 grams or per pouch, which are not the same thing. When a biscuit pack shows 140 calories per serving and the serving is listed as three biscuits but you routinely eat eight, the stated value is meaningless.
After serving size, check total sugar and sodium. Anything above 10 grams of sugar per 100 grams is high for a snack. Sodium above 600 milligrams per 100 grams is high for any food. Ingredients are listed by weight, so the first three tell you what the product mostly contains.