In my judgment, the most important thing about networking etiquette is to look for ways to be of service. When you take a service-oriented approach, people will naturally be drawn to you. Pushiness, on the other hand, drives people away.
Take interest in the other party's interests, projects, and ambitions. Figure out a way you can help. This approach works with colleagues as well as with clients.
One awesome example of service-oriented networking is Chris Guillebeau's Hundred Dollar Investment. Chris organizes an annual conference called the World Domination Summit. At the closing ceremony of this year's conference, he surprised each attendee with an envelope stuffed with one hundred dollars cash. His only request was that attendees use their hundred dollars to "do something interesting."
This stupendous display of generosity did wonders for his business. Attendees told their family and friends. They tweeted about it, blogged about it, and posted about it on Facebook. They encouraged others to attend next year's Summit. In other words, they went out of their way to promote for Chris and to bring him more paying customers. That's the power of service-oriented networking.