What Greg wrote.
Many part 91 jobs are never advertised. It is word of mouth. Someone asking a CFI or DEP they know about possible pilots. Even the girl behind the counter at an FBO.
There is a reason for this. Yes, hours on the whole give an idea of experience level that normally confers a level a safety. Yet I (and I'm sure many others), have seen high time pilots who were an accident waiting to happen- I was not sure how they made it as far as they did. I've also seen 250 hour "wonder pilots" who were great sticks, very mature and were nice guys/gals.
It is for this reason I tell my students to always assume at an airport that they are being sized up for a job. No, you don't have to wear a tie and jacket, but be presentable based upon your job and treat all the people around you with respect. I'm reminded of the "freight dog" who liked to wear offensive t-shirts, smelled as if he never bathed and treated people who worked at the FBO like garbage. Hitting on the young married girl behind the counter really po'ed people. He may have been a great pilot but he missed out on nice flying jobs without even knowing it due to his attitude.
On the flip side I once got a call from a Convair cargo operator I knew who needed an FO the next week for a ground school. At the very moment I had a sharp student taking his CMEL check ride. Really good kid who, at the age of 26 had already started two businesses and owned a trucking company with his brother. As he was finishing up the paperwork for his check ride he asked what was next. I told him to walk down the street when he was done with the DPE- he had an interview right then. The next Monday he started ground school and eventually became a captain on the Convair a few years later. All based upon the reputation I had with the cargo company owner and my knowledge of this student.