Russ Parsons of the Los Angeles Times reminds us that even though we may tend to reach for the salt shaker to add flavor to a dish, the addition of acidity can also work wonders:
Salt is a flavor potentiator—in other words, it works chemically to make other flavors taste more of themselves. Acidity works as seasoning by giving a dish backbone or structure, which allows other flavors to stand out and shine.
Parsons suggests keeping a variety of citrus fruits and vinegars on hand. Mostly important is a good red wine vinegar—he gives instructions for how to make your own out of a good bottle of wine.