How many projects have you seen where the color combination just reaches out and grabs you, yet the person can't remember the beads they used? And even with all the choices at the bead stores, it's impossible to remember and choose the same colors.
One thing I discovered when I began teaching certain patterns is that many (if not most) beaders want to create the project in the same colors you used. So I began the practice of noting which colors (by manufacturer's number) I used in the project. I keep these in a small notebook that I later transfer to a spreadsheet on the computer.
Then when I took the Diane Fitzgerald class on Gingko leaves, I found it imperative to note the colors and the sequence of colors, especially when I wanted to make a pendant and a pair of matching earrings.
This was just one use I found for making notes on my projects. I've also found that when I buy unique or unusual beads that I need to note where they came from and how much I paid for resale purposes. Of course this doesn't apply to the standard Delicas or seed beads. In my computer spreadsheet, I can also post a photo of the beads.
Tip for today: Don't forget to stretch that nylon thread before beading, other wise it can stretch and make your work sag.