At networking events appropriately position yourself. In fishing, you go to where the fish are or will be. In networking, the same logic holds. Stand where you will most likely be amongst people. Near the entrance. At the buffet or bar. Close to other high traffic areas.
If you stand outside the main stream of human flow (or worse, sit off to the side), you virtually eliminate your opportunity for having anything come from the networking event – immediately or ever.
Assuming you have positioned yourself appropriately you will encounter people. Like a parade, from your position people will go meandering by.