So - you want to know how to make a minefield...we'll...read carefully because here we go

Step 1)  Create a large brush. Texture it with the "Trigger" texture (located in the common texture folder).

Step 2)  With the brush selected, right click and select trigger-->multiple.

Step 3)  With the brush still selected press "N" and enter:

Key: targetname
Value : minefield

Step 4)   In the script file (.gsc) you need to add

maps\mp\_load::main();

And that's it

*bet you thought it would be harder

StrYdeR