Rinse out in cold water a non-reactive heavy bottom pot. Add milk and salt, stir briefly. Allow milk to heat up slowly, stirring occasionally, Soon you will notice steam forming above the surface and tiny bubbles will appear. You want it to reach 180-185 degress, near scalding temp., just before it comes to a boil. Check the temp with thermometer.
When it reaches correct temp., take the pot off the burner and add the vinegar, stir gently for only 1 minute. You will notice curds forming right away.
Cover with a clean dish towel and allow to sit undisturbed for 2 hours, or more. When it has rested take a piece of dampened cheesecloth and place in a colander. Place colander inside a larger pan or pot so it can drain. With a slotted spoon, spoon out the ricotta into the cheesecloth. Allow to drain as long as you like depending on how creamy or dry you want it to be.