Before you network, make some goals

The biggest failure that most networkers do (or rather don't do) centers around setting some goals before you go out and network. People show up, bump into other people. Certainly talk to some people that they know and maybe 1 or 2 that they don't know, pick up a few business cards and then they are done. Networking like that only can be considered "effective" if you get lucky and hit a hot prospect.
Instead I suggest you create some goals. Whether it's meet 5 new people, collect 6 business cards, talk and deepen a relationship with 2 people you've met before, or any range of goals. If you do, a couple things are going to happen, you're going to push yourself out into the group more, converse with new people more and if you meet your goal, you're going to feel better about having gone to the networking event.
Create goals, be more effective, feel better about the time spent. A very cool way to spend your time!