The Scott catalogs are a good starting point, but, for a number of countries,
are grossly inadequate. Serious collectors of Germany, for example, use the
Michel cataloguing system. You will also want a good colour guide, such as the
Schwann, to identify precisely the colours used in individual stamps. You will
also require some basic tools for handling the material, detecting watermarks,
perforation gauges, etc. I suggest contacting a good local dealer and letting
him/her advise you on requirements.