I've obtained previous jobs via both ads and networking.
One hint about networking is to always chat up the people you might consider a bit more lowly in the hierarchy of a particular firm or industry, basically, the secretaries and Administrative Assistants. They usually are in the know about everything that is going on in their workplaces and might well remember you when an opening arises, recommending you to the hiring personnel. (It doesn't hurt that many firms offer "headhunting" bonuses to their employees, either )
"One must let many things pass, without being duped"- I Ching, Hexagram 36