It's important to choose venues for the kind of networking you want to do. It's pointless going to places where you're bored or where there's little chance of meeting like-minded people. Look for presentations or conferences you're really interested in so you'll have natural sources of conversation. Big conferences can be daunting: the more unknown faces there are, the harder it is to break the ice with strangers. And people who are already acquainted tend to stick together at big conferences. Smallish gatherings are more likely to encourage exchanges among people who haven't before met. Best are experiential or interactive sessions where people can get to know a little of each other by working or playing a game together. Repeating events, like meetings of your local quality group or small conferences of enthusiasts, give you opportunities to get to know people over time and develop genuine professional relationships and friendships.
If you know in advance of specific people you want to meet, you can prepare. Look them up on the Web. There will likely be a photo, so you'll recognize them. Quite often, if you interest a speaker, she'll introduce you to others around her.
You're probably not alone if you feel socially awkward. The majority of people in our business aren't chatty extroverts by preference. (If they were, they'd be in sales.) It may make it easier for you to remember that going to a conference or listening to a speaker isn't like going to a party; it's work. As such, it's no different from the face-to-face exchanges you have in your regular work (though it may be less structured). At a professional gathering, you are bolstered by your professional competence—not undermined by any misgivings you may harbor about your social acumen.
Don't expect to carpet a place with your business cards or anticipate much benefit if you do. Be happy if you make one positive connection, and know that you'll need to take time and energy to turn that into something lasting. Pick up on something interesting the speaker says or a question a fellow session participant asks. Make it a genuine exchange. Show interest in and listen to what the other person has to say. But remember that you're not a failure if a connection doesn't happen immediately. Sometimes you'll need to meet people several times for productive conversations to ensue. Before then, you can follow up an initial meeting with an invitation to connect online.
Finally, be mindful that formal professional meetings aren't the only places for building your network. Be prepared wherever you go. Always carry business cards and be interested in what other people do for a living. Have an elevator speech ready— a quick one- or two-sentence statement that says what you do and invites questions, such as "I help organizations tailor their software testing to their business risks and opportunities."
Once you start building your network, you'll find opportunities everywhere for extending it. On a plane or train, in a taxi or elevator, you never know when you might meet someone really interesting or a person who could point you to new work adventures!