Know your area.
The lower or inland regions of California are mostly hills covered in low grass and scrub brush and dry, rocky desert effectively. Very wide open affairs most of the time. But in the mountains or higher areas its chaparral.

If you’re not familiar with it it is very dense high brush and lower trees. So there is cover and you can find a little water up there (small springs) it has the pretty much the opposite problems of the low lands (the elevation is not that much different but it’s the easiest way to describe it)

Where as down low you can just about move any which way you want here it very dense, to the point of limiting movement to trails. It is possible to smash through some of the smaller brush but the amount of time and effort is excessive. These are not something you can hack at with a machete either. Too hard to cut easily but not stiff enough to chop.

So what are some of my considerations?
Well it means that roads and trails are key features to control. it also means you will know where a group has to move though. Add to that the steep hills and canyons and it’s funnel city. That can be great for defending but you also don’t want to get yourself stuck in there either.

That dry stiff brush will leave any sign of you breaking it or disturbing it for possible months too. So whatever camp or hide or route you used can be tracked long after the fact.

Also the constant dryness is a factor. It is super easy to start a fire that will get out of control. You wouldn’t want to through a smoke out to break contact only to have yourselves get consumed but a brush fire. Same with things like tracers. “Hey the ambush went great but now we’re running for out lives into a box canyon, whoops.” But, don’t forget you could always use that against someone to your advantage too.

So what are some of your terrain considerations?