To paraphrase the immortal words of Cookie Monster, “networking is an always thing.” There’s no secret formula that, when applied, creates an awesome network for you. Like any other process, it takes a lot of small steps, and there are many tools you should use.
One opportunity which I find that far too few people use applies to lecture settings. Far too often, when some visitor—often a subject matter expert—comes to give a presentation about whatever topic, people tend to sit together with friends in the back of the room. If you’re attending this talk, it’s because the guy speaking has something to share with you, and you probably would stand to benefit from talking to him. Sitting up front means the guy/girl speaking will see your face more, and may increase the likelihood that you’ll get to talk face-to-face after the lecture, particularly if the person is going to get quickly mobbed. Most of all, though, if you sit up front you’ll be noticed as That Guy Who Sits Up Front. That can mark you as an interested person, which can be good all around.
Is this a very minor suggestion? Yes. However, this requires zero effort on your part. Give it a shot; it may help you end up meeting someone. I’d love to hear your other simple networking tips in the comments!