Paper money numismatic collection
Coins are the most common collecting objects on numismatics, banknotes are also, but rarer as they have higher value and in some countries there are also private issuers and some other type of bills such as checks, which may be issued by private finantial instituitions. Some collectors are also interested in lotery coupons, stock bonds and emergencial issues, such as the German Notgeld.

Conservation grading
Banknotes conservation grading is very important and it is usefull to indicate values for any kind for exchange or acquisition.

The International Banknote Society (IBNS) created a table with classification for conservation grading, which is used internationally, but you may find some regional variations and translations.

Numismatic catalogs
Catalogs are needed to organize any collection. There are many kinds, including general (varieties) or specific information (signatures).

Duplicates
I usually exchange my duplicates. Send me an e-mail ([email protected]) with your duplicates list and I'll send you mine.