I make room temperature cultured yogurt two ways... 1)direct-set which requires a starter for each batch and 2)propagating a mother culture which can be used for subsequent batches.
Here's the direct-set method. Add 1/16th-1/8 tsp Danisco Mesophilic Feta Culture from Homesteader Supply to 1 quart milk straight from the fridge. I prefer to use raw milk or low-temperature pasteurized milk that has only been heated to 145°, but you can use pasteurized milk... just not ultra-pasteurized. Cover the jar with a paper towel or cloth napkin secured with a rubber band. I use a lightweight, open-weave dishcloth that I cut into fourths and serged the edges. Leave on kitchen counter for 12-24 hours until it is the consistency of yogurt. The room's temperature affects the culture time, so check it sporatically throughout the culturing process for several batches. You want to catch it when the yogurt is thick but not sour, then cover with a canning lid and store in fridge. The direct-set method produces a thinner consistency than store-bought yogurt, but I don't consider it a negative attribute. If a thicker consistency is preferred, chill then strain for a couple hours in a cheesecloth-lined strainer to separate some of the whey (liquid byproduct), then whisk it briefly. (Note: I am presently researching a comparison between the live active cultures in feta starter vs. yogurt starter. Do they provide similar probiotic benefits? When I find an answer, I will post it here.)
Here's how to propagate a mother culture. Unlike the direct-set method that requires more starter powder for each batch of yogurt, once a mother culture is propagated it can be used to make subsequent batches. Making a mother culture requires that milk be sterilized (heated), but then it is added to unheated milk, so it produces room-temperature yogurt. In a pint canning jar or a similar size recycled jar, stir 1/2 tsp Cultures for Health Villi Yogurt Starter into 1/2 cup milk that has been heated to 170° then cooled to room temp. Cover the jar with a paper towel or cloth napkin secured with a rubber band. Leave on kitchen counter for 24-48 hours until it is the consistency of yogurt. Cover with a lid, then refrigerate for at least 6 hours to halt the culturing process. Now, you're ready to make a batch of yogurt. In a canning jar or recycled jar, stir 6 tbsp mother culture into 6 cups raw or pasteurized milk. In another jar, stir 2 tbsp mother culture into 2 cups sterilized milk that has been heated to 170° then cooled to room temp to make a starter for your next batch of yogurt. Cover each jar with a paper towel or cloth napkin secured with a rubber band. Leave on kitchen counter for 12-24 hours until it is the consistency of yogurt. Cover each jar with a lid, then refrigerate for at least 6 hours to halt the culturing process. (Note: To maintain the mother culture's viability and strength, it must be worked with once a week.)