What is the best way to melt chocolate?
It depends on what you're doing with the chocolate.

If temperature isn't that critical and its going to be mixed into a cake or brownies or such, then do it in the microwave.  Its simpler and as long as you don't rush it, its does a good job. Just go 10-20 seconds at a time, in bowl that doesn't hold heat well.  

If you need precise temperature controlled chocolate (for tempering perhaps), its best to use a double boiler.  The bottom pan just has steaming water - so I never really count that as a dirty dish.  With the double boiler, you get several advantages.  It won't get any hotter than the water.  It its gradual and gentle.  And you can monitor and stir as the temperature rises.  If it turns grainy, its likely a bit of water dripped in.  Depending on the top bowl on the double boiler, its possible to accidentally knock some condensation into the chocolate...and now its toast.  I use a top bowl that has a small outer lip on it to keep this from happening.