Well... whatever you do... do not put tinfoil into the microwave! Ok its a nice thing to watch the small thunderstorm it causes into the microwave, but it can damage the microwave...
When i do it i just put the weed (NOT ground or it can catch fire) on a dish and microwave it. I do not wrap it, but wrapping wouldnt do any harm. And also it would help to disguise the smell.