Step #4: Mapping
Imagine how easy it would be to unpack if you already know where the majority of your things will go? Like the floor plan, this isn't about having everything 100% set in stone. It's to give you a realistic view of what you have (seeing it in print is a big eye-opener), and gives you an idea of how much, if any, additional storage you may need.
MAPPING: Marrying step 1 + 2, give all your things a home within the home keeping in mind how you want to function in your new space. Use a copy of your proposed floor plan to draw it out (use pencil).