This is intended as more of a college-y drink, in that you can add a fairly obscene amount of alcohol without being able to taste anything but fruit juice. Its also intended to be an incredibly easy drink to make for which all of the ingredients are very easily had.
For the rum, make sure to use coconut and not normal light or dark rum, or you'll ruin it. I use the highest alcohol content coconut rum I can find (Cruzan is my favorite).
Add a lot, and then top the drink off with equal small parts of orange juice, cranberry juice, and pineapple juice. The different flavors of the juices function well to eliminate each distinguishing (and bad) taste of the alcohol in the coconut rum.
Make a big batch of it and be a straight balla.