I like Campari, it's a aperitif bitters as you may know. I got the Campari for Negronis and decided I don't really like Negronis. Americanos are OK...
But take a highball glass and fill ~3/4 full with crushed ice. Take a lime wedge and squeeze the juice over the ice. Then pour Campari about half way to taste. Fill to the top with soda water (I like Lemon Perrier) and stir. Decent spalsh of gin is optional, the gin makes it a bit more bitter which I prefer sometimes. It's a great aperitif, easy drinking on a hot day or late afternoon before dinner. It's just sweet enough without cutting out the bitterness, and the citrus makes it extra refreshing. The Campari and soda is where Campari shines for me.
