Use a quality starter culture: Live active bacteria will facilitate your yogurt, buttermilk or kefir making process. Whether you use a traditional heirloom-variety culture that can be recultured from batch-to-batch or a direct-set one-time use culture, having control over which culture you use allows you to know exactly what bacteria your finished product will contain.
Use high quality milk: Culturing your own dairy products makes is much more affordable to use high quality milk. For example, organic yogurt in the grocery store generally costs $.09-$.19 oz. but when you only need to buy the milk (once you have the starter culture), you can take the cost of organic yogurt down to $.04 oz. A huge savings! It only takes a few batches of yogurt to completely recoup the cost of the starter culture. The savings for buttermilk and kefir can be even more dramatic! In addition, it can be difficult, if not impossible, to find healthy yogurt, buttermilk and kefir made with the type of milk you might prefer (non-homogenized, locally sourced, raw, etc.) so making your own dairy products allows you much more freedom to choose the quality of your milk across several dimensions.
Leave out the additives and stabilizers: Most commercial dairy products contain additives and stabilizers to thicken the product, change the texture or sweeten the product. Most of these additives and stabilizers are chemical based and even those that are not (sugar and powdered milk) aren’t particularly good for you. Making truly natural and healthy yogurt, buttermilk and kefir allows you to consume these products without all the unhealthy extras.