tempering chocolate means to melt it ever so slowly so it never goes above 100 - 102 degrees farenheight.
That pretty much means the microwave it not going to work. A double boiler will if you really, really have patience and go slowly.
Alton Brown uses a household heating pad in a bowl then the chocolate in another bowl inside that. I've done it this way twice. It takes a long time, but it works. keep a thermometer handy and don't let the temp get too high.