I made a spreadsheet on excel with seperate pages for each type of product. (ie, necklaces, bracelets, earrings...) It has my product numbers, an item description, wholesale and retail price, and cost to make item and finally a date slot for when the item sells (hopefully, at some point here...)
For my product numbers I use a letter (ie N=necklace, E=earrings ect) and then 1,2,3 ect as I build stock. I just stick a slip of paper into each bag with the product number on it. ( so if you look at my listing and see N23 at the bottom of the listing then it is the 23rd necklace I listed)
It may not be the best way, but it is working so far :)