Michael Arrington's tips on how to network are basic, but sorely needed by the nerd community:
1. Never underestimate the power of an introduction. A mutual friend who introduces you by email or in person is far more effective than a cold self-introduction at a crowded event. Approaching someone randomly should be your last option.
2. Don't approach someone when they are clearly in the middle of something. If I'm throwing a conference, there likely isn't any time at all that is appropriate to approach me. But there are 2,000 other people there you can hit up who aren't as busy as I am at that time. Hit me up at the event that I'm attending but not running.
3. Don't approach someone when they are in the middle of a mob trying to get their attention. This is usually after a speaker has just left a stage, and everyone hits them at once. If you must grab them then because you have no other way of meeting them, make it very, very quick and aim for nothing more than their business card so you can email them later.
4. If you get someone's business card, never call them. That mobile phone number isn't for you, the person who just met them. A random call to their cell phone is never welcome. Send an email. (I kinda messed up on this one. Larry Hagman gave me his card once, but it didn't have his email... so I never called! Ha.)
5. When you approach someone, don't assume they know you even if they do. You see them across the room, note them, approach them and say hello. You've had a few moments to think about it, but all they see is a face in front of them, a thrust out hand and a "hello!" It's not reasonable for them to decide if they know you, remember your name and where you work in a half-moment.
Instead, say "Hey Bob, It's Mike from TechCrunch, good to see you again" slowly and clearly. You've just told them your name, where you work, and the fact that you've previously met. Trust me, they are thankful for all that information, and everything will go smoothly from there.
6. If you forget to tell them who you are, don't get offended if they don't know. There will likely be a few sentences of very unspecific conversation as they try to remember any detail about you, or even if they've met you before. If they start off with "how are you?" or "what do you think about the event?" then things are going badly. They should be asking "how'd that financing with Sequoia go?" or something much more specific.
7. If you've blown it to this point, for the love of God fix it. Drop in something like "yeah, since I met you at the whatever event we've been rocking at TechCrunch. We finally launched that new blog on bicycles." Bam, you've saved the situation. Notice how much better the conversation goes from there.
8. Look for body language. If you pay attention you can tell how engaged they are. If they aren't engaged (looking away, never talking, etc.) don't try too hard to get them to focus. Instead, move on to what you want. Get their card, see if a meeting or a call is possible and ask for the best way to make that happen. Some people think the more time they spend with a person the more likely they'll get what they want. In reality, it's the opposite. Don't take time just because they are too polite to end the conversation.
By this time, you're probably asking: am I a geek, dweeb, dork or nerd?
Thanks to John Hagel for clarifying: