First you need a die, whatever it could be. Even a *cough* counterfeit will do. (img shown at bottom)
<- Next you borrow that hammer off my avatar to strike planchets and volia! A nice "coin" there! Of course, the sickle is there for you to behead yourself if you are planning to counterfeit some coins
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Ok, leaving the joke part aside, I am sure there are a fair bit of sites that does give details of how coins / medals are made. Even the US mint do give a general idea of how coins are made.
http://www.usmint.gov/faqs/circulating_coi...fm?action=coins