Networking is about starting within your sphere of influence. If you have no network start with friends and family. Ask "who do you know at company X or in industry Y that I could talk to about roles [A,B,C] at company X or how I could better align myself for a role in the industry or at company X." (I hope that makes sense.)
Example: "Hi Mark! We both worked at company A and now you're at Apple! That's so dope! I'm reaching out because I am looking for a change and I really think it'd be fun to work at Apple. How do you like it there? I know the place is super secretive so maybe generally can you tell me how working there has helped you grow in our field?
I saw these two Apple roles A and B links here and here. Could you help me talk to the hiring manager to really see exactly what they want from a candidate, what problems they're trying to solve? Would you be willing to refer me to the role?
Thanks,
John Doe"
Then work your way up. So say you have a role and have folks you worked with that have moved on to companies you think are cool. If you are a worker with a good reputation of being productive etc., reach out to them (even better if you were friends before they left) because you have the current company in common it will serve as a conversation starter. Ask them about their current role, what they like, how they've grown, and if there's a role there that you want to interview for ask them for advice about it and even for a referral.
You can repeat this process for folks that share your same university, church, other social group etc. But that's basically how I approach networking. Oh and one more thing, nobody likes being a stepping stone or being used. So in all these interactions be honest, open, and be genuine. Legit take interest in them and their success and they will reciprocate.
Good luck! Feel free to reach out (email in bio) if you wanna chat more. And if you want to migrate to Berlin I have some pointers there, too as that's what I did. I am originally from Portland, Oregon.