Then Hidden Job Market is simply jobs that are in the minds of Hiring Managers that may or may not ever get posted. All jobs that do get posted are former Hidden Market Jobs. So, wouldn't you rather be first on their mind, rather than come into consideration after the posting. Also, if you wait, you will have more competition.
You can’t control MANY aspects of your job search but you DO have extensive control over your networking efforts! By properly networking with individuals at your target corporations, you will have first hand knowledge about new opportunities, and also become aware of their problems or challenges and are ready to explain how you can solve them.
Remember the old saying, “It’s not what you know, it’s who you know”. That is no longer valid… “It’s not what you know, or who you know, it’s who knows you”
You need to have a “Top of Mind” presence with people you are networking with (peers, Hiring Managers, Recruiters, key contacts at your targeted companies, etc…). When they hear of something in your area, do they think of you?
You should concentrate on creating relationships (over resume submissions) and the relationships will create opportunities. I think most people are fixated on submitting their resume just because that is what they are used to and are comfortable with, but times have changed… find and build relationships with the Hiring Managers. After all, 60-80% of positions are filled via Networking. Only 4-7% are filled via the job boards!