I use an old 1 inch square grid D&D map that is inside a poster frame so I can write on it with wet / dry erase markers. I use a 10 meter (~30 feet) per square scale outside and a 2 meter (~5 feet) scale inside. PCs and important NPCs have painted 1:72nd scale minis. Others use unpainted minis or dice... I have a whole handful of
large Red D6s with the Yellow Star for generic Ivan and several end to end to make an improv tank or APC.
For a fixed battle, I'll draw up a map of the area before hand on
gaming paper like I did for the POW camp assault in
my blog at the bottom.
For indoor maps, I'll sketch out a floor plan and use piles of dice to indicate features such as beds, tables, whatever.
Outdoor maps are looser. I sketch in major terrain features in a general way. "This is an area of woods, this is a ridge, here's the road, and any wrecks." But I don't detail trees or dips or whatnot. I assume if you're in the right area you can grab cover behind a tree or fold in the ground.
Anyway that's my system... YMMV