A lot of people ask me how to get started in this hobby. Well, it starts with research. I don't know how or why, but somehow I stumbled upon a great site about radomes and I was fascinated. I started reading about the radomes and gap filler sites and my natural curiosity took over from there. Once I found out that there were significant military sites all around me, I had to go see them.
Make a list of the ones that are interesting to you and then check them out with Google and Google Earth. There's no sense getting all excited about seeing a site, driving three hours to it and then finding out all you can do is take a picture of the gate because it's still active or closed off to the public. Take notes about any interesting features that are worth checking out, especially things that might make that particular site unique from all others. Also, talk to your fellow Cold War Relic geeks and see if they have something in particular they might like to see. These are the guys that will help you the most in your travels, so a little quid pro quo never hurts.
Once you've done research at home, get yourself a good map (in Maine you can't beat the DeLorme Gazetteer), plenty of food and water, a truck with a full tank of gas (leave the Prius at home--it won't make it through the woods) and hit the road. Don't forget to bring along bug spray, sun block, comfortable shoes, dry socks, a jacket and all those other things your mom wouldn't want you to leave the house without. It's more fun to bring friends, but if you go alone, make sure someone knows where you're going.
Please keep in mind that many sites are on private property or lands maintained for public use by paper companies and other land owners. Respect the area when you visit it. Get land-owner permission if it's private property. Spray painting graffiti, leaving beer cans and bottles, breaking windows and leaving trash behind will do nothing but ensure that these sites are closed off for the rest of us. DO NOT F*CK UP THE HOBBY FOR THE REST OF US. SERIOUSLY.