Simple cocktail method, fill the glass full with ice, pour desired amount of Absolut Ruby Red Vodka, add Squirt, leave some space for cranberry juice.
Substitutions could include: unflavored vodka instead of Ruby Red(however not as grapefruity) or Grafs 50/50 pop instead of Squirt. The key is to have grapefruit pop. I have not yet tried grapefruit juice, but suspect the absense of carbonation would make the drink suffer.