Making a Good Impression
Networking is all about making a good impression: If you don't come off well, no one will want to help you land a job. This means you have to be courteous and appreciative of any time and information people offer you, even if you don't think it will help you. Send thank you notes. Follow up on advice. Be on time for any appointments. Be grateful for anything and everything you're offered. The bottom line is, professionals are busy people and if someone takes the time to help you -- whether it's giving you advice via email or passing your resume along to human resources -- and feels you don't seem appreciative, they will get annoyed.
I've heard of several occasions where professionals I know got annoyed because someone asked them for advice, they gave it, and then the person never followed up to thank them. You don't want to burn any bridges, especially when you're just starting out, so make sure to thank everyone you meet/talk to, no matter how valuable you found what they had to say is.
Don't Get Frustrated
I always found that, in some ways, networking -- especially when you're looking for a job -- can be more frustrating than interviewing. I remember talking to myriad people who had jobs that i didn't particularly think i wanted only to find out the conversation didn't lead to much. Now I realize that I went into these networking situations with the wrong attitude. Networking, espeically the kind you'll do during your first intensive job hunt, is all about getting information and getting your name out there. You need to keep that in mind and keep a positive attitude. You also need to have faith that you will make connections networking that very well may become valuable years down the line. I know I got contacted about job openings years after meeting with some people.
Further Reading:
Many universities and graduate schools have some good, basic info on how to network as a recent grad. This piece on Duke University's website offers some good tips about how to start networking in your job search.
You can also find some more tips on networking do's and don'ts in this article from a career site.