However, if you are seriously collecting art, then it is important to keep track of your collection with something other than paper and pen - after all, we are living in the digital age now.
Coming to our rescue are art collection management systems! Designed to keep track of sales, purchases, leads, reports, and much more, software systems like these can be tailored to your needs. There are a lot of them out there, some are free and online, while some of the more advanced systems cost a little more. Below are some links:
ArtSystems - a pretty advanced system for galleries and larger collections
ArtBase - excellent - many NYC galleries use this
My Art Collection - a little less sophisticated but good for smaller collections