Updating existing products' info from CJ datafeed updates

Question

I know variations on this question have been asked, but I think this is specific enough to merit a new question.

When I receive an updated data feed from Commission Junction I dump it all into a database. Then those products become searchable and selectable for use on our site. However, since all of the data used seems to be fluid, how can I update the products I have saved on the site with the new information? How can I match new info to existing products?

I'm hoping that someone has been doing this long enough to be able to say certain fields rarely change and can generally be relied upon, etc. etc.

Thank you!