What salt actually does
Salt suppresses bitterness, enhances sweetness and amplifies every other flavour in a dish. It also draws water from cells via osmosis, which affects texture. Understanding both effects — flavour and texture — tells you when to add it. According to Serious Eats, seasoning at multiple stages is more effective than one heavy hand at the end.
The timing rules
Meat and fish
Salt right before cooking — or at least 45 minutes before. The worst window is 5–40 minutes before: moisture is drawn out but has not had time to be reabsorbed. Dry-brining (salting 1–24 hours ahead, uncovered in the fridge) is the best approach for thick steaks and roasts — see the Serious Eats comparison.
Pasta and grains
Salt the cooking water generously before it boils. The water is absorbed during cooking; salt added after sits only on the surface. Roughly 10 g per litre is a good starting point. See al dente in the glossary.
Vegetables
For sweating: salt immediately to draw moisture and speed softening. For roasting: salt just before the oven, otherwise moisture escapes before heat can evaporate it, and the vegetables steam. For salads: just before serving.
Bread dough
Salt goes in after flour and water are combined, not with the yeast. Direct contact between salt and yeast kills the yeast before it activates. In most formulas, 2% salt to flour weight is standard. See the baker's percentage guide.
Season in layers, taste as you go
Professional cooks season at every stage — when sweating onions, when adding stock, when finishing the sauce — tasting each time. This builds flavour through the dish rather than correcting at the end. The Escoffier School emphasises tasting as a discipline, not an afterthought.