It is hard for me to be more helpful. I have been so privileged that my experience unlikely typical.

A college friend, got me the interview that got me my first job. I did not even send a copy of my resume, I brought a copy to the interview that we shared. I basically tagged along with him to his interview and got interviewed too. They hired us both. I was his best man at his wedding.

At that job I was mentored by top notch experienced practitioners who referred me to colleagues as I advanced to learn from other mentors until I became the mentor. By that time I had a stack of business card of most of the talent in my profession. I was not actively building a network, it just happened organically.

Since I graduated in 1981 and got my first job I have only sent out two job applications, one to Dynetics and the other to SpaceX both after I got laid-off in 2011. A colleagued called me out of the blue and talked me into joining his start-up.