For my U.S. collection I use a free Mystic Catalog. If I have it in MNH condition I put little star next to the Scott number. If I have it in any other form of mint other than MNH I put a check next to the Scott Number. If it is in used condition I circle the Scott number. If it is a space filler I put a line in the Circled Scott Number. And if I need the stamp I leave the Scott number untouched. It works very well and the Mystic catalog is very detailed....and free.
Here is the online catalog
http://www.mysticstampcatalog.com/Here is where you can order you free catalog from Mystic.
http://www.mysticstamp.com/adlookup...lookup=SC88H