As far as I can see, absolutely nothing beats this 12 part blog from Personal Development author Steve Pavlina, on the topic of professional networking. It’s thorough, frank and packed with well articulated old and new ideas. You can read it in parts or take an hour to read the lot. If you implement some of his ideas, I can almost guarantee a fast return on investment.
http://www.stevepavlina.com/blog/2009/07/how-to-network-with-busy-people/