I've been gaming since I was 12 years old. Since the beginning, I've tried many many different terrain techniques and methods. Starting at the beginning and working through the list:
Painted green pingpong table with lichen/twig trees, fabric roads, ceiling tile hills (UGLY)
Felt covering (UGLY)
Ceiling Tile modular squares for 1/285th armor (Brittle, limited set up)
Styrofoam modular squares (Messy to make, easily damaged. Blch)
Particle board hexes (about 8" across, all cut by hand on power mitre box. Great flexibility, even being very particular, there were inevitably large gaps on the board. Almost impossible to have exactly the "right" piece when coming up with layouts. I still have several large boxes of these...can't bear to throw them away).
Flocked indoor/outdoor carpet (very durable, but I learned to detest "plop on" rivers and roads. I just can't stand seeing rivers and roads sliding all over during the course of game play).
Felt over hills, loose flock (VERY messy. Had too much of a skirmish game feel to me - in my opinion, everything else in a miniature wargame is scaled down, and this terrain was too much 1:1 type scale. Flock got EVERYWHERE. This one was short lived!)
And finally - my ultimate system - 12" squares made from 1/8" thick floor tiles. This stuff is really great to use - you cut it by scoring and snapping, it doesn't warp. With the finish technique that I developed, its very hard wearing and durable. I'll start posting "how I did it" posts this week. It gives me the flexibility to do virtually any terrain combination or arrangement that I want. I'll post how I make the basic squares, hill sections, river and road sections.
With that said - here's some more photos of the last game we played: