In military science, it's well understood that intelligence wins wars.
Very few job seekers take advantage of the obvious corollary here. Everything you can learn — not just about specific employers and the opportunities they have open, but about how employers and recruiters see the world they operate in — is invaluable.
Researching employers is so obvious I won't dwell on it. But the other dimension is worth considering. In managing your career (or simply looking for a job) wouldn't it be invaluable to get inside the heads of the people you're talking to? The people who will make the hiring decisions?
It's not difficult to do. In fact, you're one click away. ERE.net is a wonderful resource for recruiters and employers. That makes it a wonderful resource for smart job seekers!