There isn't a universal way of feeding a cat properly. As with humans, it depends on the stage of the pet's life, its health and mental condition, physical condition, level of activity, its environment and many other factors.
Fortunately, giving them poor quality food is no longer a common mistake. It is also essential to always buy food according to the needs of your pet. Just choose an honest manufacturer and then find the right product. Granules and canned food are now made to fit all the normal stages of a cat's life, taking into account its nutritional needs, whether it be a kitten, senior cat, pregnant cat, neutered cat or outdoor cat. It is no longer necessary to balance the nutrient and vitamin ratio. You can read how to recognize good food here.
However, we often still let our pets overeat. I read somewhere that up to 35% of cats are obese. Obesity significantly shortens the quality and length of their life. If your cat is prone to obesity and overeating, don't underestimate it. Replace its granules with reduced calorie granules, i.e. "light" granules (sometimes it's necessary to put the cat on a special veterinary diet), don't give it unlimited access to food and motivate it to get some exercise. You can read more in the article about cat obesity.
Another common mistake is suddenly changing their food. Even if you decide to buy better cat food, this should not happen overnight. Your cat's digestion is set to a certain ratio of nutrients. If you suddenly give her something else, her body won't be able to cope with it and she may have digestive problems. Imagine if you would suddenly start eating only Indian food; your stomach wouldn't be too happy either. The change must take place slowly, gradually increasing the proportion of new food in the old food.
It used to be normal to give cats cow's milk, but fortunately most of us now know that they cannot digest it, namely the lactose it contains. Although cats like the taste, the moment of pleasure is replaced with diarrhea and other digestive problems. Therefore, if we want to treat our cat with milk, we should buy special cat milk.
The latest trend is vegetarian and vegan cat food. However, cats are naturally carnivorous, so it logically makes sense that they simply cannot thrive on such a diet.
The opposite extreme is only feeding them meat. Cats are exclusive carnivores, but they consume their prey (mainly herbivores) along with the content of their stomach. They therefore won't find all the necessary substances in pure muscle meat.
Another mistake is feeding them with only dry food, i.e. granules. Cats often don't drink much, and their kidneys start to fail with insufficient water intake. Such a fluid-depleted diet may thus contribute to dehydration and other health problems. In this case you should at least make sure that your pet drinks enough water.
It's also wrong to feed your cat dog granules. I wrote more on this topic in the article “The differences between dog and cat food“. Can you think of another mistake that cat owners often make, albeit with good intentions?