I'll be honest, I don't pack for anything until the night before or day of my trip. I have always been like that, but since getting older and having a much larger range of wardrobe options to choose from I've in the past few years written out a "Pack List" with the basic necessities and think on it for a few days to determine which shirts, dresses and shoes I'll be cramming into my suitcase.
Five pairs of shoes for a three day vacation, sounds about right. No matter how long the trip I inevitably fill my suitcase to the brim, never fails. Oh, and the palm trees are just to make you jealous.