RDF by itself doesn't have a syntax; it's just a data model.
However, the most popular expression of RDF, at least as expressed in W3C documents, seems to be the RDF/XML syntax.
The RDF Core WG's revised RDF/XML syntax spec is the best authority on RDF/XML syntax.
There are some more (rough) notes on RDF's syntax in the FOAF wiki.
Excellent and short RDF tutorial on XULplanet for developers, hers is the related part: RDF-XML Syntax