Opening the book…
The last thing you add to a dish often does the most for it, because a final touch of fat, acid, or freshness hits the palate directly instead of being muted by cooking. A knob of butter swirled into a sauce off the heat gives it gloss and body; a drizzle of good olive oil over a soup adds richness and aroma no amount of cooking-in could; a squeeze of lemon or a scatter of fresh herbs cuts through and lifts the whole. These finishing moves are what home cooks most often skip and what most reliably close the gap between their food and food that tastes considered. Cooking builds the base; finishing puts the highlight on top, and the highlight is often what people actually taste and remember.
Keep good finishing ingredients ready and separate from cooking ones: a nice olive oil, cold butter, lemons, fresh soft herbs, flaky salt, a hard cheese to grate. Add fat off the heat and swirl or stir it in for richness and shine, as in mounting a sauce with butter. Add acid and delicate herbs at the very last moment, since heat dulls their brightness. Think in contrasts: something crunchy on something soft, something bright on something rich, something fresh on something deep. Taste after finishing and make the final seasoning call, because these additions change the balance.
Not every dish wants finishing; some are complete and gilding them just muddies a clean flavor. Delicate dishes can be overwhelmed by an assertive oil or too many herbs, so restraint matters. And finishing fats and oils are best kept uncooked for their flavor, so save the good olive oil for the drizzle and cook with the plain one.