Networking is collecting contacts. Relationships are what happens when you actually follow up.

Collecting contacts is easy and mostly useless. A name in your phone does nothing until something has passed between you, and what converts one into the other is almost always an unglamorous message a week later. Most people never send it, which is exactly why sending it works. A relationship starts at the second contact, not the first.

After you meet somebody worth knowing, write within a few days and mention the specific thing you talked about. Ask one real question, or send them something they would find interesting. Then do it again in a couple of months without needing anything.