Actually, there's no need for tears at all, it's a doddle making your own kefir, but why waste a good title?

How to make your own kefir

The first thing you need are some kefir grains, which are little clusters of culture (bacterial, not Proust-reading). If you can't find someone with spares to give you they're easily and cheaply bought as mail order on t'internet.

If you buy them, the grains will come with instructions, which will be variations on the theme of "put the grains in milk and wait".