1 - 2 lb tempered chocolate (chocolate usually comes tempered when purchased)
Avoid tempering chocolate on excessively hot or humid days.
Chop the chocolate into small pieces. This can be messy and/or dangerous. I find that a large serrated knife does a nice job. Reserve about 1/4 of the chocolate chunks and set to the side. Simmer hot water in a double boiler and add 3/4 of your chocolate to the double boiler and melt until the chocolate reaches about 110 °F. Take your time and don't get the chocolate too hot.
You can also use a microwave instead of a double boiler by using short, 10 second bursts, stirring frequently with a brief rest between bursts to allow the heat to evenly spread. If your microwave has a low setting, you may be able to increase the length of cooking—just be careful as overheated chocolate can scorch and the flavor will be compromised.
Remove the double boiler from heat and stir in the remaining 1/4 of chocolate chunks. Stir until completely melted. Check the temperature of your chocolate and let it cool to 80 °F. At this point, you need to slowly heat the chocolate again. Do this in short bursts by returning the double boiler to the hot water for a moment, stirring, and then removing to stir some more. Repeat this process until you bring the temperature to 88 - 91 °F for dark chocolate or 84 - 87 °F for milk or white chocolate.
Test the temper by smearing some chocolate on waxpaper and observing. It should cool to a nice sheen and break with a crisp snap. If gray or tan streaks appear, you will need to repeat the entire process.
Proceed to dip your treats carefully monitoring temperature. Return the chocolate to the double boiler with hot water as needed to maintain temperature. If the chocolate gets more than a few degrees outside the range specified, you risk losing both your's and the chocolate's temper. Cooled truffle centers can really bring the temperature down fast if you are dipping quickly, so pay attention, take your time and monitor your dipped chocolates for any streaks.
Alternate method: Use a tempering machine and follow manufacturer's instructions. ;-)