Here's my process:
1. Heat 1 quart of milk to at least 185 degrees. (In the old days of unpasteurized milk, they suggested bringing the milk to a boil. I did this once and had burned milk on the bottom of the pan. If you want more information about the "whys" of milk temperature, follow this link.)
2. Cool the milk to 110 degrees. My yogurt maker has a scoop with a built-in thermometer that is marked with a range of 100 - 110 degrees. At this point I add the starter with my scoop, which is about 2 tablespoons.
3. Put the yogurt in the small 6 oz. cups and place in the yogurt maker. When the yogurt maker is plugged in, it keeps the yogurt at a constant temperature. I've never measured mine, but the pros say the temperature should stay between 85 and 100 degrees.
4. Incubate for 10 hours, according to the directions for my 2 makers.
5. Refrigerate for a couple hours before eating. This further allows the yogurt to set.
6. I strain about half of my batch to make a Greek-like yogurt. Homemade yogurt is a little runnier than commercial yogurt because it doesn't have gelatin or pectin. I use a paper coffee filter and a mesh colander to strain out the whey. I like the result of this over using multiple layers of cheese cloth or even a cotton tea towel. The resulting whey has NO milk in it, which by the way makes it impossible to use for making ricotta cheese. Sometimes I let the yogurt strain for 20 minutes and sometimes for 2 hours. I like to scrape the sides and bottom of the filter; this seems to help the straining process.
Lots of websites give more detailed information and may answer specific technical questions. I'm more of an experimental cook who likes to view directions/recipes as suggestions as opposed to commands.
Next up: making ricotta cheese!