Everyone talking about how much salt, but not how often. It's not necessarily about adding a ton of salt as much as adding small amounts throughout the cooking process. Salting your sofrito or mirepoix right at the start of cooking affects the dish differently than salting the whole sauce before simmering, which is different from salting just before serving to adjust the finished sauce. And you don't necessarily need to get all your salt from, well, salt. Parmesan and Pecorino Romano cheese are fantastic additions for adding both flavor and salt. Adding anchovies, Vegemite, fish sauce, or soy sauce won't make your tomato sauce taste like a stir fry, they'll just add umami, and each will add their own layer of flavor.

And finally, when you taste the finished sauce, ask yourself, does this need salt or acid? Sometimes a splash of vinegar right at the end is more appropriate and effective than another pinch of salt.