how?

a condensation of
http://ar.essortment.com/makingyogurt_rxua.htm

First of all, you need a yogurt culture (bacteria). I believe that you can buy them (at a health food store maybe?), or - as the link says - you can use commercial yogurt (unflavoured and unpasteurised) instead.

After you've made your first batch you can save a bit and use it for culture.

Boil milk to 110 degrees F and get rid of any skin. Whisk your yogurt culture until it's watery and mix it with the milk. Incubate it at 110 for a couple of hours in an oven and put it in the fridge to set.

It won't have preservatives, so it will go bad quickly and it will probably be more liquid-y than the stuff you buy at a store.

[This message has been edited by Craftian (edited 04-04-2002).]