If you choose to pin (or staple) something - pin it in the selvage - so if it rusts or something - the only mark will be on the very edge. It probably is a good idea to keep track of how much you have and how much it cost.
Some people keep notebooks (3-ring binder types)- they cut off a tiny scrap and staple it to a piece of notebook paper with relevant information. Where, when, how much, maybe why?
Since I started buying quilting fabric, I've learned a few things:
1) That they keep making new prints
2) That they discontinue some prints - usually one I only bought a little of and wish I had bought more!
If it is a print that you truly, truly, truly love, buy at least 3 yards of it. Even it it's kind of spendy at the time.