To fit in with my Urban Space Marine theme, I wanted to put some barbed or razor wire on bases. Thing is, I had no idea how to do it until I got this idea after looking at GW's Razor Wire that they sell... taking soldering wire and twisting it. Here's my method:
1) Grab hand-drill and solder (powered drill just puts out too much torque and it's hard to gauge where your wire is. I twisted mine too much sometimes that it just stretched and broke)
2) Cut soldering wire and fold in half. Put the folded end into the drill and secure tightly.
3) Tie loose ends of soldering wire to a fixed position (I use my lamp post) and begin to twist. It is very important you pull the solder so it is nice and tight.
4) Twist until you get it looking roughly like this picture.
5) Cut it from your fixed position and take the end of a brush or pen and begin wrapping it around.
6) There we go... now to make it look like barbed or razor wire (whichever you prefer).
Take pieces of solder and wrap it twice around equidistant (or whatever your eye thinks is equidistant... this is a poor example of that :p) points and then cut so a small bit hangs off each end. Do this as many times as desired.
Take a hobby knife and carefully cut about half-way into the solder and then twist your knife upwards to get the shard to stick out. I do this all around the wire and it looks pretty good (in my opinion at least).
All you half to remember is be careful not to overdo it. It's a really easy and fast method and works great. Just remember that when you're done you must coat the wire in superglue to make sure it's nice and hardened, otherwise your hardwork will fall apart!
Hope you enjoyed this short tutorial and expect more in the future!