For context, I am planning to switch jobs in the near future and I've been to a few networking events in my city, but I'm not sure if they're useful. It also seems to me that people don't remember each other from these events, so it's pretty pointless in the long run. I'm happy to be corrected, though.
Having said that, I have over 10 years of experience in the software industry, and my network "size" is essentially zero. I get along well with my peers when at job, but once I switch to another job, the only "link" between my old peers and me is linkedin. I have never relied on others to get a job, I have never recommended anyone... not because I don't like to do those things, but simply because I could get a job the usual way (Apply button). I've attended a couple of conferences (but only because the company was paying and because I was going already with some of my peers).
I don't keep the contact with the people I met at university either (I live now in another country, although this sounds more like an excuse in the era of the internet).
I want to build a network of people working on cool stuff, even (especially?) if it's for fun. I'm trying to lessen the loaded buzzword nature of what networking means to me for this to happen. People are social creatures after all.
Apparently it is really important, because I suck at it and I'm professionally stunted.
If you need a new job you can reach out to them and they will help. If you have plan you have people to talk about and maybe find someone willing to help.
IMHO, networking is good for finding job opportunities and candidates you might not have found otherwise. And a good recomendation can sometimes get you past a resume screening, which is helpful when your resume isn't well tuned to the jobs you want. You've still got to pass the interview, probably.
Again, IMHO, it would be better to focus on intentionally networking with your organic network than developing an artificial network.
Finding contact information for people you enjoyed working with and sending them a message like. "Hey X, I enjoyed working with you at $company, I was wondering what you're up to now and if there's any openings? ktnxbye" Take notes and pass along news about openings or interest in moving that you think are relevant to others. When you have notes, you can ask questions like how's it going at company you last heard they were working... and it feels more connected and less forced. If you're not actively searching for new work, still try to still put in the effort to reach out to people you'll want to ask when you do search. Probably between once a year and once every 5 years is good to keep contacts up to date.
Start by sending to people you actually enjoyed working with and/or think did good work, and increase the scope until you're messaging the people you were surprised managed to get hired -- chances are they managed to get hired somewhere else and that place must not have high standards ;)
I'd say that among the highest paid people in the world, only a small percentage of them have some special specific skill, but ALL of them have huge, high-valued networks which served them very well during their ascent to the top.
The issue is you can't just be naïve and try to meet as many people as possible like some sort of heuristic hustle agent. The best networks are formed via shared deep experiences, ala:
1. College alumni
2. Company alumni
3. Romantic relationships
4. Childhood friends
5. Strong friendships via serendipitous happenstance
Any other case you can only get good results from networking if you already have some 99.9th percentile product or skill.
As far as how to do it, just do your work well, treat people well, and be the kind of person they want on their teams in the future.