Here’s a photo essay on building a 15mm machine gun nest.
Big Lee’s Miniature Adventures has an illustrated tutorial on making model 15mm vegetable fields from corded dormats.
Bunkermeister offers Quick and Simple Wargames Rules For Everything.
Small World Productions has a tutorial on making a “hex” based terrain table for Command and Colors.
The Frozen Gamer has an article on making asphalt roads from vinyl strips.