There are long lists of reasons why dairy is bad and all that stuff (and some people do react to all forms of dairy), however, most of those reasons apply to pasteurised (read: cooked to death) milk and milk products.
The list in favour for RAW dairy is much more rewarding. The only negative is "Oh, what about the bacteria?!" The fancy thing about dairy is that God thought about that long before people did. The milk contains a whole bunch of natural ingredients that not only take care of this problem in the milk, but are a great benefit to the consumer (human, baby cow/goat) as well. Funny though this gets melted away during the pasteurisation process. Even still,of this sterilised milk there are known outbreaks of harmful bacteria, Salmonella being among them.
I could go on and on about the benefits of raw milk (which most people of a certain age grew up on and are probably much more suited to fight the diseases that who knows how the next generation will fair), but then I would never get to the recipe. The internet is loaded with information on raw milk.
Do not expect raw yogurt to be sweet, it isn't. I like to use it primarily as a substitute for sour cream. I would also add it to smoothies, but since it is in short supply I save it away for use as sour cream for stuff like tacos, borscht, and zucchini pancakes. We have a billy goat now, so hopefully in a few months there will be more milk to go around. I will have to see later how goat's milk yogurt turns out.
But for now...
The amount of milk that is so generously given to me by a friend is 1 1/2 litres. I shake it to mix the cream that has separated back into the milk. Then I divide this evenly into two clean, sterile mason jars. I place these jars in a pot filled with water on the stove, and slowly heat to 110 - 110 F, using a dairy (or candy) thermometer. Make sure to stir the milk occasionally, as the milk at the bottom of the jar will heat faster.
An alternative way is to heat the milk up to 180 F, then cool it down to 110, but I personally want to get all the benefits possible from this wonderful milk.
The milk should be fine to touch with your bare hands - not too hot. Take the jars out of the pot (for ease) and add some yoghurt starter. This yoghurt will be from a previous batch of yoghurt or for your very first batch a GOOD yoghurt bought from a store. I found a nice homogenised yoghurt from a health food store (amazingly enough), and used that for my first batch. Then I made sure to keep some of that batch for the next batch. I add a few tablespoons into each jar, mixing well to incorporate.
Once this is done, I put the lids on an return to my pot on the stove. Monitoring the temperature with the dairy thermometer, I keep the water up to 95 F (more or less) and cover with a cloth to keep the jars warm. You will need to turn on and off the burner every once in a while to maintain the temperature. Keep warm for 8 hours. The yoghurt will then be ready for the fridge for whenever it is needed.
The resulting yoghurt will have a lot of liquid in it. But this is very valuable. Strain the yoghurt quickly (not overnight as to make cream cheese) through a cloth bag. The resulting liquid is the whey which is great for making lacto-fermented ketchup (recipe to come). I keep a bit of the whey in the yoghurt to keep the consistancy that I like - you could make it a very thick or thin yoghurt, depending on your choice.