Easiest place to get it is from the product you want to produce. For example, if you want to make yogurt then grab a little bit of the leftover yogurt in your

Easiest place to get it is from the product you want to produce. For example, if you want to make yogurt then grab a little bit of the leftover yogurt in your fridge, drop a dollop of it in, and viola, it'll start the yogurtification process. You can also rely on the open-air bacteria for some culturing, but the results can be all over the place. This is how a lot of sites suggest starting sour dough.