The latest version of this document is available at http://www.unidata.ucar.edu/netcdf/docs/netcdf-install.
This document contains instructions for building and installing the netCDF package from source on various platforms. Prebuilt binary releases are (or soon will be) available for various platforms from http://www.unidata.ucar.edu/downloads/netcdf/index.jsp.
A good general tutorial on how software is built from source on Linux platforms can me found at http://www.tuxfiles.org/linuxhelp/softinstall.html.