Here’s a good video tutorial on making the sort of terraced wargames hills which are not particularly realistic, but which are eminently practical from a gaming perspective.
modeling
Working With Mantic’s 20th Century Red Brick Terrain
For their Mars Attacks game, Mantic released sets of 20th century style brick ruins. They’re good looking, but with a little work can be even better.
Making Hedges With Plasticard and Clump Foliage
Here’s another tutorial on making hedges — useful for lots of different settings.
Making Ruined Roads from Vinyl/Lino Tiles
The Tabletop Terrain blog has a useful article on using vinyl/linoleum tiles to make roads appropriate for a combat zone or post-apocalypse setting.
How To Make Craters
This video tutorial teaches a technique for making craters. It’s a useful thing for modern, post modern and full-blown science fiction games.