I find the safest method to be the oven. Water is the big enemy of chocolate, even a drop or two will ruin a batch, so when I want to be safe, I melt my chocolate in the oven. I use an oven proof ceramic bowl. I place the chopped cooking chocolate in the bowl, turn the oven to its lowest setting (mine is 180°F) and place the bowl in the oven. Check it every three minutes by stirring it with a very dry spoon or one of those oven proof silicone spatulas. In most ovens it should not take more than ten minutes. Once out of the oven continue to stir, as the bowl will be a bit too hot for the chocolate.
Chocolate may melt in an oven and still retain its shape, that it why you have to test by stirring. Most cooking chocolates melt at about 100°F, which makes melting them in the microwave just as tricky as doing it on an improvised double boiler. After you get the hang of it, any method should work (in a hurry, I do it straight on the stovetop by putting the pan on and off the burner).