I recently discovered that several of my brothers-in-arms are wargaming fanatics just like myself. I was invited to their private wargame fest at a local hotel, where eight of them were holed up during a weekend pass. As they were occupied trying to glue their new figures together, I decided to run out and pick up some basic supplies to make them some terrain. Here you can see three different types of brush I found at a local hobby store, and the best part is that all of it was on sale for cheap!
I also purchased an inexpensive pair of clippers to cut the vegetation down, and they would also be useful for trimming figures from their sprue.
Next, I picked up a small brick of air-dry clay, and worked it until I had some nice globs into which I could stick the pieces of recently trimmed brush. I then squashed the clay so as to make a nice solid base for the vegetation, which could later be sand-coated and painted over with the three-color drybrush technique.
I also found some of those nice, large and dark corkboard tiles for a low price as well. So I picked up a package and broke them off into pieces, gluing them onto each other in order to make some ruins.
As you can see, the various pieces start to make the bare tabletop less so with very little effort.
Finally, I showed them my technique for churning out cheap razor wire. The bottom line is you can easily produce a massive amount of nice terrain on short notice, as long as you have a craft store nearby!