Don’t cook on full power – set your microwave to half power (or medium).  This lessens the chance of the chocolate heating too quickly and “seizing”. Heat slowly – melt the chocolate in 20-30 second intervals for the first minute, then in 15 second intervals after that, stirring after each cooking interval.  It takes longer, but trust me, it’s worth it. Add a bit of oil – one of my favorite tricks is to add a little bit (about a tablespoon or so) of vegetable oil to the chocolate before melting.  I don’t think I’ve ever had seized or scorched chocolate when following the microwave tips and this one!