I am awful at making fudge, but found this wonderful--may I add foolproof?--recipe at Cooking for Engineers (http://www.cookingforengineers.com/):
In a double boiler, melt 3 cups of chocolate chips (do measure, you need more than 1 small package. You also may combine the flavors of your choice), 4 tablespoons of butter, and one can of condensed milk. Let melt and combine until the texture is creamy and shiny. Pour onto greased Pyrex and chill in the refrigerator. Yum!