The boys from Thomson Whisky make a Negroni and Boulevardier:

Typically you should use 20-30mls per part, depending on how big your glass is. Fill a large mixing glass with ice, add the ingredients in the order above and then fill the rest of the glass with ice and begin stirring. Use a metal straw to taste intermittently while stirring until it's just right (you'll know).

Strain into a tumbler filled with ice, and garnish with orange peel (make sure to give it a twist and wipe it around the brim of the glass). Alternatively. the Boulevardier can be served in a chilled martini glass sans ice (same garnish).