The step of networking that many scientists overlook is ensuring that you actively maintain the relationships that you have worked so hard to start. When you get home from a conference within a few days you should actively take steps to stay in touch with the contacts that you’ve made. This is as easy as sending a quick and professional email. It can be as simple as stating that you enjoyed meeting that person, that you found your conversations useful, or thanking them for sharing a technique. If you offered to send someone reagents, a journal article, or data you should do so promptly when you return home. For more formal interactions (e.g. job interviews, invitations to give plenary talks, etc.) I think that the old-school idea of sending a hand-written thank-you note is appropriate and appreciated.
Once you return from a conference you should also go over any notes that you took during talks, discussions, and poster presentations. These insights might influence your own research directions, or perhaps you have a follow-up question that you need to contact someone about. Pass along any useful information that you picked up at the conference to others in your research group or offer to summarize the major ideas presented at the conference to your lab group or department.
These are ways to maintain both your external network with scientists outside your institution as well as strengthening your relationships with researchers you interact with every day. Now that you have more experience with networking, please “pay it forward” and mentor other scientists who could use your new found wisdom and advice.