1. Making it all about you. If you're only in touch when you want something, you'll quickly turn off your contacts. Instead, turn this around and think about how you can help others, whether it's connecting them to a job opportunity or forwarding an interesting article. Finding ways to be a helpful resource to others can be the best way to get help in return.
2. Not forming real relationships. Networking isn't about making as many contacts as possible; it's about making quality contacts. If you look at people as merely a way to expand your circle, your efforts will probably fall flat. Instead, make it your goal to build genuine relationships.
3. Acting entitled to someone's time or access to their connections. Giving you those things are favors, and you significantly lower your chances of getting them if you don't reflect an understanding of that. Always make it clear that you know you're asking for a favor, that you'd be grateful for any help they can provide, and that you'll understand if it's not possible.
4. Not thinking about what the other person wants. Before you ask someone to help you, stop and think about what they might hope to get out of it. Generally, people doing you a networking favor would like to feel that you recognize and appreciate their efforts—and perhaps even that you admire their work, if it's true. Take the time to tell them that.
5. Misappropriating someone else's contacts for yourself. One reader told me about a contact who connected with her on Facebook, then promptly sent friend requests to all her Facebook friends who were connected to the field that he was trying to get into. "That's obnoxious enough on its own, but many of them were my social friends, not professional contacts, and on the wrong side of the country anyway," she said later. "Not cool, guy."
6. Offering help and then disappearing. If you offer to introduce someone to a contact or put in a good word with an employer, make sure you follow through. The other person is counting on you, and it's frustrating to be on the receiving end of an offer that never materializes.
7. Lying. If you say, "Jane Smith told me to call you," and it turns out that Jane Smith didn't say any such thing, you'll have permanently burned your bridge with both parties.
8. Not saying thank you. Say thank you every time someone helps you, and you'll increase your chances of getting their help in the future. Whether it's taking your call, connecting you with someone else, or forwarding you a job lead, you should always send a thank-you note.
9. Not following up. It's frustrating to spend time giving someone advice and then never hear how their situation turned out. Make sure that you check back in with people who spent time talking with you, and let them know where you ended up.
10. Not networking. Believe it or not, not networking can frustrate your contacts just as much as everything above. One reader told me, "I hate finding out months down the road that someone could have either provided a service I needed or have been just the right fit for some job or gig I knew of, but they were too shy to open their mouth about a potentially mutually beneficial arrangement. It's intimidating to give yourself props, but it can't be more intimidating than missing out on an opportunity, can it?"
Alison Green writes the popular Ask a Manager blog, where she dispenses advice on career, job search, and management issues. She's also the co-author of Managing to Change the World: The Nonprofit Manager's Guide to Getting Results, and former chief of staff of a successful nonprofit organization, where she oversaw day-to-day staff management, hiring, firing, and employee development.