Making homemade yogurt, whether greek or not, is super easy! And, it will save you a boatload of money compared to purchasing it at the store.
In a large pot heat a gallon of milk to 180 degrees, using a candy thermometer to monitor the temperature. After the milk reaches 180 degrees, remove your pot from the heat and allow to cool to 100 degrees.
Mix in 1/4 c. yogurt (greek or regular plain with live and active cultures) and whisk through the milk.
Pour the milk into a crock pot and allow to set on warm for 8-12 hours.
Strain off the thick layer of whey that will form on top (save it for other uses!) and you have regular yogurt.
If you used greek yogurt for your starter, place a tea towel in a colander and place you yogurt in the colander. Strain off all of the way over 1-4 hours. Greek yogurt will look very lumpy and need to be blended in your blender to make it a smooth consistency.