Since you don't indicate you have any technical background or experience at all, I'll assume you have none, and proceed from that assumption. You'll want to start gently, in the Brainbench "Test Center > Information Technology > Systems and Network Administration > Network Administration" area, where the coverage of Networking Concepts, Network Monitoring, IP Routing & Switching, and Network Technical Support provide excellent starting points. After that, you'll want to pursue and obtain the CompTIA Network+ certification, followed by a vendor cert sequence of your choice--could be a Microsoft MCSA/MCSE, Novell CNA/CNE, or Cisco CCNA/CCNP, Linux+ followed by SAIR/GNU or LPI Linux or Red Hat RHCE, or something similar. That should keep you busy for about 2 - 2.5 years and teach you much of what you need to know.
At the same time, obtaining hands-on knowledge and experience is absolutely essential. Set up a minimal 2-node network at home and learn how to perform the kinds of installation, set-up, and configuration tasks you'll need to know to do a networking job. Volunteer at local schools, churches, or charities to help with networking tasks, or try to talk your way into unpaid help with networking tasks (like system or network upgrades) in your current job (if you have one). Anything you can do to learn by experience (and talk about during job interviews) will make you more attractive and therefore employable when you seek to find work in this field.
Good luck! A word of warning as well: certs are no longer enough to guarantee employment during these tough economic times. That's why I urge you to do everything possible to garner some experience to go along with your credentials.
This was first published in September 2002