So much of what has been said is valid for one area or type of brush and not another. I burn a lot and have no problem getting stuff to grow where the piles were--actually they grow better because competition is reduced--seeds & weeds burned up--and nutrients, except nitrogen, increase from ashes of the burned stuff. The nitrogen goes into the air. This has been true in NW Oregon where I live now as well as in western Montana. Actually the heat doesn't go very far into the soil, just an inch or two.
Cedar and cut Scotch broom burn like a torch.
I like using a sprayer to put fuel on the fire because you can put a film over almost everything and have little waste. If you throw it on from a bucket or fuel can, a lot just washes down to the ground.
Never, never, never use gasoline to start your pile. The fumes will drift and if you start the fire from downwind or downhill, you will be inside the explosion area. It's just a quick whoosh, but you don't want to be there. A mix of 1/3 gasoline and 2/3 diesel works OK.
A fire line around the pile isn't a bad idea, but if the area around the pile is wet it may not be necessary. The line doesn't have to be very wide--I have fought forest fires where we dug a line only a few inches wide because there wasn't much fuel. The more fuel, the wider the line. Just have to get down to mineral soil. If you put your line next to the pile, you'll want a wider line. Go out 10 feet and the line can be pretty narrow--unless you have a monster pile.
If burning anywhere near a building, be sure the gutters are clean or wet.
Propane burners use a lot of propane.
You can take a toilet paper roll, dip it in diesel and put it under a tall and dense part of the pile and light it. It will burn for quite a while, but most of the heat goes straight up, which is why you put it under a tall part of the pile. Or as someone mentioned, use a newspaper.
Big stuff burns best if close together to radiate heat back & forth.
You want fines--little stuff, twigs and needles in abundance to start the fire. Here I can start a fire easily if I have a lot of dry Doug fir needles. But hardwoods with no leaves? No way. The have to dry a very long time compared to the DF.