The one lesson I've always kept in mind during social situations: be a good listener.
People at networking events specifically tend to come with their own agenda. They're never really talking to you, it's like they're waiting for you to finish or say a keyword for them to start their sales pitch. Not to say having an elevator pitch ready is a bad thing, just don't keep that gun cocked on every unsuspecting subject.
Ask them where they're from, what they do, and how they do it (obviously not prying into proprietary practices). And really listen. Be genuinely interested. People will love that they can practice their sales pitch on you, and by the end of a 5-10 minute little info blast from them, they tend to turn to you and ask: "So what do you do?". That's when it's your turn to be ready to drop your pitch, but make it relevant, now knowing what they do and how you can possible integrate with them.
Make sure to exchange business cards. And then when you get home (or within the week), prepare personal emails for each person following up on the meeting. It reinforces the relationship and shows them they weren't just a one night stand at a conference 😉 Then follow them on LinkedIn / social media and start using your social currency to show them some love. It's the easiest and healthiest way to grow a network.