Heat your milk between 180 and 190°F (82 to 88°C). Stir from time to time.
When your milk reaches the right temperature, let cool in the corner until you read 110°F (43°C) on your thermometer.
Mix your starter (about 1 gram for 1L of milk) or 1 cup of your market yogurt(without flavor), I save the cup from my last batch to your milk until it's completely dissolved.
Put in your yogurt maker and let sit for 8 hours, when it's done put it in the fridge for another 4 hours.