I wear an apron and not a lab coat, so when I learned the process for making yogurt at home, I was fascinated. All you need is milk and a small container of yogurt and science does the rest. I made my first batch expecting to be disappointed. The opposite was true. For the first time, I actually liked the taste of plain yogurt. Now I make yogurt once a week. Specifically, I make nonfat greek yogurt using a yogurt maker. Here's how I do it.

Step 1: Tools & Ingredients

Ingredients

Yogurt Starter (1/2 cup store bought plain yogurt or 1/2 cup saved yogurt from your last homemade batch)
5 1/2 cups milk (not ultra-pasteurized)

Set time: 9 hours.
Strain in refrigerator: 1 hour.
Estimated yield: 1 3/4 cups greek yogurt.
Estimated nutritional value per 6 oz serving: 100 calories, 0g fat. (per documentation from Dash Greek Yogurt Maker).

Tools

Pan. Non stick is recommended for easy cleanup.
Cooking Thermometer. I use the kind that you can clamp to the pan
Yogurt maker (Optional. See step 5)
Ice bath (optional)

Tips

If you prefer thicker yogurt, mix 3/4 cup powdered milk with the 5 1/2 cups milk
Take the yogurt starter out of the refrigerator at the start of the process. It will need to be at room temperature when you get to the mixing step.

Step 2: Heat Milk

Heat milk to 180 F. This takes me about 45 minutes. The milk shouldn't boil, so I use a med-low setting. I use a thermometer that clips to the pan so I can instantly see the progress. Note the thermometer in the picture. It has 180 degrees marked. I find this really helpful.

During this step, you will likely see milk skin form. If this bothers you it is easy to remove with a fork. Otherwise, you can just stir it into the milk.

Step 3: Cool Milk

Remove the milk from the stove and place it in an ice bath to cool to 110 degrees F. 110 is marked on the thermometer for this step also. With an ice bath, this step takes about 10 minutes. Keep an eye on it. You don't want it to go below 110 before the next step.

Tips

An ice bath is handy to speed up the process, but it is optional. Alternatively, just let is cool naturally.

Step 4: Mix Milk and Culture

Make sure the starter is at room temperature. Add it to the yogurt maker container. Add milk. Mix gently.

Step 5: Keep It Warm and Wait

Now everything is in place. The milk has been prepped with conditions that are ideal for the bacteria in the starter to grow. A yogurt maker will be used during this step. It will maintain the proper temperature and keep track of the time it has been culturing. The folks who make the yogurt maker recommend culturing 9 hours when using skim milk. This generally works for me, but if it is firm enough, I find that 8 hours is enough. The longer it cultures, the more sour and firm it will be.

Note the photo with the spoon resting on the yogurt. This shows the firmness of the yogurt. Note the liquid in and around the spoon. That's whey. The whey will be removed in the next step.

Tips

Since the goal of this step is to maintain a warm temperature, a yogurt maker isn't actually necessary. I am told that some people put it in the oven with the oven light on and this keeps it warm enough. Others put it in a container and keep it warm with a blanket. I like to keep things simple, so I prefer a yogurt maker.
Since the bacteria eats the lactose, culturing longer means less lactose. That's why some people with lactose issues can tolerate yogurt, but not milk.

Step 6: Strain

When making regular yogurt, straining is not applicable. However, since this is Greek yogurt, this step involves using an ultra fine mesh strainer or cheesecloth to strain the liquid from the yogurt. The liquid is a watery yellow substance called whey. Since this is nonfat yogurt, there will be more whey than fatter yogurts. A strainer and a second container come with my yogurt maker. This allows me to easily strain from one container to the next. I generally end up with about a pint of whey.

Tips

Save the whey in a jar and put it in the refrigerator. It is good in soups and smoothies.
For best results, put in the refrigerator while straining. Set your clock for an hour. If you strain for longer, too much liquid will be removed and you will have something that resembles cream cheese.

Step 7: Store

Store in jars or an air-tight plastic container. I like to make berry jam and put 2 tablespoons at the bottom of a mason jar. Top it with yogurt and you have yourself a container of fruit at the bottom yogurt. Yum.