ooor....heat the milk before adding the cocoa and sugar- if it's just 'normal' cocoa, I use equal parts cocoa to sugar in full milk, lots of both... nice and sweet. Oh, and as N2L said, boiling is bad!!! Maybe add some cinnamon???

The best hot chocolate I have ever made was melting a block of dark chocolate in a pot, and stirring through a pot of cream, then as it warmed stirring through some sugar til it dissolved. Oh. My. God. Richest hot chocolate ever!!!!