Fill a shaker with ice cubes. Add all ingredients. Shake and strain into a chilled cocktail glass.
The salt rim is quite easy to make. Take a wedge of lime or lemon, and wet the rim of the glass with it. Pour some salt (any salt will do but a flake salt is a bit more chic) -- on a small plate and simply dip the glass rim in it. Voilà -- you just gave a glass the characteristic, cool Salty Dog look.