After the show or material shopping... for those of you who are taking it from hobby to business, my practice is to photograph and catalog everything I've purchased during the show.
It's good practice to make note right away, even though you might be exhausted, of who you buy from, what the material is, and any specific details about that material that you might want to use in your finished jewelry description.
Also, make note of the price you paid and the retail value of the gemstone in today's market. This will help you later when it's wrapped and ready for selling.
Many gemstones will come with the carrot weight, dimensions, and description of where it's from or what it is on the back of the box. If it does not, I will generally carry a small notebook so that I can make these notes. It's usually months later when I have finished jewelry from these pieces, and I may or may not remember these details.
I photograph measurements and weights as this is an easier way to keep my inventory details without my rushed hand writing and notes to rely on later.