Ingredient notes:

Onion, celery, carrots: Now is the time to use your knife skills. Dice everything evenly in small ¼-inch dices. The size uniformity of these ingredients will allow them to cook evenly and will produce a more enjoyable texture. By the way, this combination of ingredients, cooked in olive oil and seasoned with salt and pepper, is called a soffritto and is the base of many Italian dishes.
Tomatoes are not a main ingredient in the sauce – you add a bit of it for taste but it is a meat sauce, first and foremost.
Meats: Use lean ground meat (for a special treat, ask your butcher to chop the meats coarsely – 1/3 inch thick) and best-quality pancetta.
Milk: Yes, milk is the surprise ingredient responsible for producing a more orange than red sauce (it also makes the meat more tender).
Broth: Although the registered 1982 recipe doesn’t include broth, most recipes I’ve encountered include some instead of water. It makes more sense to me taste-wise to choose beef over chicken broth.
Seasoning: This recipe (perhaps surprisingly) doesn’t contain any aromatic herbs or spices. It is frowned upon to add bay leaves or red pepper flakes. The only flavoring in this recipe is sea salt and black pepper. It is highly recommended to use sea or kosher salt as it lends a more refined taste than regular table salt.
Pasta: This is a hearty sauce that should be eaten on pasta that can support its weight: it is often served with the wide and flat tagliatelle (fresh or dry).
Cheese: Please – please – use only freshly grated authentic parmigiano-reggiano. It makes all the difference in the world.
Method: Finally, note that this sauce doesn’t like to be rushed. Some recipes with offer shortcuts but the only way to allow the flavors to develop fully and the sauce to become so rich is a very long simmering – and I mean, 4 hours long. The base of the recipe isn’t complicated or time-consuming to make and the rest is just passive time in the kitchen. You start a bit batch, stir in once in a while and enjoy for many meals to come.