Homemade yogurt sounds like one of those intimidating things that you need special skills and a "yogurt maker" for. I have a recipe that is nice and simple and you can do it without a bunch of special anything!
Here are the supplies and ingredients that you will need:
-1/2 c good quality commercial plain yogurt
Heat the milk to 180 degrees on the stove. A double boiler is recommended but I don't have one and we do fine without it. I set the burner to med-high and check the milk's temperature every 5 minutes until it reaches 180.
Pull the milk off the stove and let it cool until it reaches 110 degrees. This can take a while. I would check the temperature every twenty minutes or so until it reaches 110. Once it gets to 110 put in the yogurt and whisk. (Don't rush this step, if you put in the yogurt when it's above 110 you could kill the enzymes and you won't get good yogurt.)
Next, place the yogurt in a shallow glass, enamel, or stainless steel container. Cover the container and place in a warm oven (a gas oven with a pilot light or electirc oven pre-heated to warm and then turned off) overnight.
In the morning, transfer to the refrigerator.