Comment by johnnyanmac

If it's "previous employers", it might already be too late. Networking basically comes down to "being confortable about people who you know will vouch for you". Especially helpful if they are in power to hire or you suspect they will be one day.

As the other reply said, it really comes down to "hang out with them outside of work". Not often, just enough that you know more about the person than what's related to the job. Working colleagues already work with you so they can speak to your technical skill.

Outside of work colleague, you gotta meet people. So find soke tech communities locally or some FOSS projects you can contribute to.

In any case, it's a slow process and stuff rarely happens immediately. It's something best to do when you don't need a job.