Then bring it to almost a boil. I think the exact temp is about 185 degrees, but I am so used to just turning it off when I see bubbles (or forget about it and then remember when I see bubbles!) This is just to sterilize the milk.
Let the milk cool. This I do measure with my wonderful kitchen probe thermometer. I think the range you want it down to is 95-115 or so. I shoot for 110 degrees. Once it's down to about 110, pour it into the warming vessel of your choice. I've seen people use crockpots wrapped in towels, jars in insulated coolers, and I use an actual yogurt maker/warmer someone gave me. The milk just has to stay warm somehow for awhile.
Once it's in the warmer, I add 2 tablespoons of yogurt as a starter (just slowly plop it in, no stirring). Cover and let sit anywhere from 10-24 hours. I shoot for 12-16, but the longer it sits, the stronger the "zing." I've messed up many a batch of yogurt, so here's some tips:
- Don't forget about it while its cooling :)
- Don't add to much starter (for some this is bad, I'm not exactly sure why, but trust me)
- After it's done, put it straight in the fridge. Don't stir it. Once cool, if you like watery yogurt, stir it up or pour off the whey for varying levels of thickness
- Don't unplug it and forget about it on the counter :)