This has become default nowadays than any other medium.
1) Look for local chapters, groups and events relevant to your field of interest. They may have periodic meetings or those similar to you in terms of interest in expanding their networks.
2) If there are companies you are interested in or certain fields, as people in these groups post on Li, ask them questions through comments. Engage them on something they are already interested in. then you can seek to connect with them. Then you can evaluate whether you can deepen your engagement through exploratory meetings.
You always want to start networking before you need it. By networking when you have no ulterior motive, you can begin to build relationships and a reputation for being generous rather than self-serving. Have a plan, get a clear understanding of skills, strengths and talents you can bring to the table and how you can help others. Never dismiss others as unimportant, always look at everyone equally.