Dog food packaging is designed to sell, not to inform. The front of the bag is marketing; the useful information is on the back, and once you know where to look it takes about a minute to judge a food fairly.
First, the ingredient list. It is ordered by weight, so the first two or three ingredients are what the food mostly is. A named protein — chicken, lamb, fish — near the top is a good sign. Vague terms like 'meat derivatives' tell you little.
Second, the guaranteed analysis, which lists protein, fat and fibre. Match these to your dog's life stage and activity rather than chasing the highest protein number on the shelf. Third, the feeding guide — the right food fed in the wrong amount still leads to a fat or thin dog.
Fourth, look for a line confirming the food is complete and balanced for your dog's life stage. 'Complete' means it can be fed on its own; 'complementary' means it cannot. If you are unsure what suits your dog, ask — honest advice about what your pet actually needs is worth more than any claim on the front of the bag.