Add
vinegar and 1 teaspoon salt to boiling water. Remove pot from heat. With lip of measuring cup just above surface of water, gently tip eggs into water, one at a time, leaving space between them. Cover pot and let stand until whites closest to yolks are just set and opaque, about 3 minutes. If after 3 minutes whites are not set, let stand in water, checking every 30 seconds, until eggs reach desired doneness. (For medium-cooked yolks, let eggs sit in pot, covered, for 4 minutes, then begin checking for doneness.)