Put 8 cups of milk into a crock pot on low for 2 and a half hours. Turn the crock pot off and wait 3 hours. Put in a half cup of starter. Plain dannon or activia yogurt seems to work the best. You only need to buy it once though, because for all later batches you can just set aside a half cup of your finished product.
After putting in the starter, let it sit in the crock pot over night, or at least 9 hours.
At this point you have yogurt.