I make mine using the stovetop/oven with great results.
Set the oven to preheat to the lowest setting you possibly can. Get out an individual carton of plain yogurt. eat half :-) put the other half in a bowl.
Dump milk in an ovenproof saucepan or pot and heat to 190 F, stirring. Once it reaches temp turn the oven OFF (still nothing in it) and move the milk off the burner. Stirring frequently, get it down to 110-115 F.
Once its cooled, put a small amount of milk in with the yogurt and stir gently - do not whisk. Then put the whole thing back in with the milk and stir. Put a lid on and put it in the (off) oven overnight. I leave the oven light on, it is supposed to add a tiny bit of heat but mostly it reminds me that there is yogurt in the oven! You may need to play with the timing of heating the oven etc, it may not even be really necessary if the house is warm, but I always do it.