The library is full of books on postcards, and you can visit
www.postcardcollector.org for random information and the benefits of membership.
But it isn't clear what you mean by identification. I have 30K postcards, and doubt that I have ever identified even one of them. I research publishers and artists; I find similar cards on Delcampe and
ebay to estimate value; I watch closely for philatelic aspects; and I pay attention to addressees and sometimes Google the name(s). But I don't "identify" them. If you want to establish a value, use retail pricelists and auction results, but it's a tedious process.
Another good source is
www.marylmartin.com -- I have known the family for 30 years. In the past 5 years, I have sold a single card for over $300, and sold 1400 mixed cards for $125 postpaid, so there's a wide range of prices and interests out there.
Regardless of what informations you discover, I strongly encourage you to NEVER write on the card (or on the backs of stamps either).
Here is the way I advertise small lots of cards (on another website), in this case, four
1905 cards from South Africa:
http://www.stampboards.com/viewtopi...f=27&t=37593