I hate to admit it, but I had to look up "PLN" to see what it meant...and then I did the whole "face-palm" thing because, while I didn't recognize the acronym for a "Professional Learning Network" (PLN), I do have several.
Our school as been part of a Professional Learning Community for many years. That means that we get into groups like our Content Teams to share ideas and give help. We have Content Teams, Vertical Teams, and Lead Teams. All these teams form our League of Professional Teachers. We work together to make decisions that shape our curriculum, focus, and plans for the year.
Another network I use for professional wisdom and help would be Pinterest and Facebook. I know those don't normally sound like places to network, but they really do have ways to connect. On Pinterest I follow boards and people when I see that they have Pins that I could use in my own classrooms, and the network grows when I see that they follow me, too.
Facebook, too, is a networking place for me since I can connect with former colleagues and teachers and, if I need to, ask questions and get advice. I am on Twitter and follow various blogs, but I know I don't use them to my advantage in this area. I am still new to the technology, but I am learning how to use it more and more.