How are mammograms done on men?

Same as for women: Men have breast tissue like women, although less of it. A mammogram is done the same way-- by compressing the breast between two flat plates and taking an X-ray of the breast tissue.

Same as women: There is no difference in the technique, only the volume of tissue available to be imaged.

The exact same: technique as with females. A mammogram can be performed on virtually anyone with even minimal tissue in the breast regions.