For anyone who is not already a patent agent with a lot of experience of the PCT, a short paper on the WIPO website entitled "Protecting your Inventions Abroad" is invaluable. It starts off with the really basic stuff such as "I have an invention. How can I protect it in several countries?" and
"What is the Patent Cooperation Treaty (PCT)?" to more substantial information on filing costs, priority, searches and sources of information.
This is so good that I am putting a link to this article from our public access blog nipc Invention.