The key to painless unpacking is to over-prepare. You can create a number key, use color-coded tape, or cover each box with detailed Sharpie notes.
However you decide to do it, make sure you record the following three things:

  1. Which room the box goes in
  2. A general description of what’s inside the box
  3. A detailed list of the box’s contents

That way you won’t have to dig through three boxes marked “Kitchen Utensils” just to find your whisk.