I used a combination of recipe/ advice in making yogurt. I took the basic method from Simply in Season, but used the more comprehensive discussion from Super Baby Food to inform what I did.
The S in S recipe suggests using a 2 quart (64 ounce) Thermos to keep the yogurt warm while it is incubating. So make sure you have one of those handy. Mine happens to be 3/4 the size recommended in the recipe, so I adjusted amounts accordingly. You, of course, can do the same. You will also need a candy themometer -- a themometer that can clip onto the side of a pot.
Heat a big pot of water to boiling to sterilize the spoon, pot and thermometer you will use. Keep it at a low boil to use in a later step.
Pour out eight cups of milk. I chose to use raw milk despite Angela's warnings. I knew I would be trying to grow bacteria, which I hoped might have more of a chance in raw milk. I also knew I would be heating it, which supposedly kills off harmful bacteria. You could find all sorts of Web pages proclaiming the benefits and/or detriments of raw milk and/ or raw milk yogurt. I just wanted to give it a try. My raw milk comes from Frank White http://agmap.psu.edu/Businesses/3280 in Monogahela.
Heat milk in a saucepan to 185 degrees. Stir constantly and use low heat. The milk should not boil. Scald the milk, which means let tiny bubbles form on the outer rim of the milk where it touches the sides of the saucepan. I used a candy themometer to help me estimate the correct temperature.
The book suggested pouring the milk into another container after it reaches 185 degrees. I skipped that and just turned off the heat and left the themometer in until the themometer and the milk reached about 112 degrees.
Pour boiling water into the Thermos and close the lid.
Measure four tablespoons, i.e. 1/4 cup, of yogurt "starter" so that it can rise to room temperature. Yogurt starter is yogurt with live, active yogurt cultures. The books suggested using store bought yogurt for your "starter."
Also, according to the suggestion, I froze one tablespoon portions of fresh, store-bought yogurt in an ice cube tray. After they were frozen, I then emptied the yogurt cubes and put them in a freezer-safe plastic zipper bag and put them back in the freezer to use later.
When the milk has cooled to 112 degrees, add the "starter" to it and stir.
Pour the water out of the Thermos and pour in the milk and yogurt combination. Close it up tight and put it someplace warm. Maybe wrap it in a blanket or heating pad or something and then don't move it for four to six hours.
It was tricky for me to keep the yogurt warm. It is supposed to incubate at 110-115 degrees for hours. In truth, I have no idea what the temperature was. I did not want to open the Thermos and let out any heat. Our house has plenty of cold spots and very few warm ones, so I put the Thermos in front of the warmest spot in our house.
After carefully maintaining a temperature of 110-115 degrees for 4 to 6 hours check on the yogurt. When you feel it is thick enough, it is done. If you leave it for longer, it can get more sour and you should add additional sweetener. In my case, I had to go to do kid stuff and just stopped the process at 4 1/2 hours. The result was less than ideal.
The yogurt seemed runny to me. Probably because 1) raw milk does that and 2) I don't think I let it incubate long enough and 3) it may not have been at a warm enough temperature.
At this point, you can add honey and fruit or whatever, but stir it gently. Good luck. It's not hard to get a taste and smell like real yogurt, but in my brief experience, it is more difficult to get the right consistency.