One thing that I would like to mention before I get everyone enthusiastic over fermenting foods and drinks, is a word about sanitation. While the yeasts and beneficial bacteria that develop with fermenting foods are good for you, there are other microbes that are not. Therefore, it is mandatory that you sanitize your bottles, jars and equipment that you use and store your ferments in a safe place, away from any possibly harmful influences s/a garbage bins, moldy window sills, etc. It's probably also a good idea to boil your water first before using it in a recipe.
I always wash my glassware thoroughly and then use the sanitizing cycle of the dishwasher to finalize the wash. I also boil my jars/bottles for at least 20 minutes before I fill them. There's also a product called Star San which is used by brewers and cheese makers that will get your equipment sani-clean.
This is a really important step, especially if you are using animal milk products, which, if not properly handled, can cause some deadly bacteria such as listeria to develop.