Kit Kat: suck all the chocolate around the wafer first.
Mars: nibble everything around the caramel first then allow caramel to melt in mouth.
Galaxy Bar and all other pure chocolate bars: relax in a comfortable chair, listen to techno music, eat the chocolate with eyes closed slowly, then lick all the chocolate left on fingers.
Best practice is when chocolate is when the chocolate is left out of the fridge for a while before eating.