From Delivering Happiness: A Path to Passion, Profits and Purpose by Tony Hsieh.
I personally really dislike "business networking" events. At almost every one of these events, it seems like the goal is to walk around and find people to trade business cards with, with the hope of meeting someone who can help you out in business and in exchange you can help that person out somehow. I generally try to avoid those types of events, and I rarely carry any business cards around with me.
Instead, I really prefer to focus on just building relationships and getting to know people as just people, regardless of their position in the business world or even if they're not from the business world. I believe that there's something interesting about anyone and everyone -- you just have to figure out what that something is. If anything, I've found that it's more interesting to build relationships with people that are not in the business world because they almost always can offer unique perspectives and insights, and also because those relationships tend to be more genuine.
If you are able to figure out how to be truly interested in someone you meet, with the goal of building up a friendship instead of trying to get something out of that person, the funny thing is that almost always, something happens later down the line that ends up benefiting either your business or yourself personally.
I don't really know why this happens or why it works, but it seems that the benefit from getting to know someone on a personal level usually happens 2-3 years after you started working on building the relationship. And it's usually something that you could not have possibly predicted would have happened at the beginning of the relationship. For example, maybe your friend's sister's neighbor was just hired as the VP of a company that you've been trying to get in touch with, or maybe someone you met 2 years ago now has a new tennis partner who would be the perfect person for that job opening you've been trying to fill for the past 6 months.
Zappos.com has been around for over 10 years now. We grew from no sales in 1999 to over $1 billion in gross merchandise sales in 2008. In looking back at the major turning points in the history of the company, it seems that most of them were the result of pure luck. Things happened that we could not have possibly predicted, but they were the result of relationships that we had started building 2-3 years earlier.
So my advice is to stop trying to "network" in the traditional business sense, and instead just try to build up the number and depth of your friendships, where the friendship itself is its own reward. The more diverse your set of friendships are, the more likely you'll derive both personal and business benefits from your friendships later down the road. You won't know exactly what those benefits will be, but if your friendships are genuine, those benefits will magically appear 2-3 years later down the road.