Season soups during cooking as directed, then taste the finished soup before serving to adjust the seasoning with salt and pepper as needed. Adding a small amount of fresh lemon juice or vinegar just before serving can brighten the flavor of many soups. Use only a few drops at a time, tasting as you go. Some soups are enriched with heavy (double) cream, sour cream, yogurt, butter, or olive oil just before serving. Stir these ingredients in gradually, and don’t allow the soup to boil if you are adding sour cream or yogurt, which can curdle at high temperatures. Add garnishes after dividing the soup in serving bowls.