I wrote down how much wire, what gauge, lengths of sides. Even the tools I used. Everything I would need to recreate it. I started in pencil to get the rough draft down. Next I will re-do it in pen and add a set of basic sample earrings to the card for reference. Then I can add it to my design book for future reference.
The glory of this system, as you polish the idea and refine it and change it, you can continue to add notes. You'll be able to whip out a new set of earrings in just moments.