If you have not yet read it, I'd advise you read the JDBC API Documentation (supplied with Sun's JDK), and the JDBC Specification. Both are available from http://java.sun.com/products/jdbc/index.html.
http://jdbc.postgresql.org contains updated information not included in this document, and also includes precompiled drivers.