1-First, heat the milk in a saucepan over medium heat until it reaches 180°F (82°C) to kill any unwanted bacteria and prepare it for culturing, while also considering the effective range of 30 to 45 degrees Celsius (86 to 113 degrees Fahrenheit) for optimal fermentation as noted in yogurt production details.

2-Second, remove the milk from heat and let it cool to 110°F (43°C), a temperature ideal for beneficial bacteria to thrive.

3-Third, stir in the plain yogurt starter thoroughly to distribute live cultures evenly, initiating the conversion of milk sugars into lactic acid.

4-Fourth, pour the mixture into a sterile container, cover it, and incubate at 110°F (43°C) for 6-12 hours, aligning with the 4 to 12 hours required for fermentation to achieve a thick texture and tart flavor. Higher temperatures may speed up the process but could result in lumpiness or whey separation, so monitor carefully.

5-Fifth, check for desired thickness and taste; longer incubation produces tangier yogurt. For a thicker consistency like Greek yogurt, strain the yogurt to remove whey after fermentation. Final step: refrigerate the yogurt for at least 2 hours to stop fermentation and enhance texture before serving, adapting for dietary needs as discussed.