If you have a double boiler, more power to you! If you don't, you can set up a simple "bain-marie:"
Rest a metal bowl on a saucepan with 1 inch of water in bottom.
Make sure the bottom of the bowl is at least 1 inch above the surface of the water - not resting in the water.
Using chopped chocolate or chocolate wafers, reserve a quarter of the amount of chocolate in a separate bowl to use as a "seed" later.
Grab a silicone spatula and a good thermometer, and you're ready to rock.