it's a game of minesweeper. falling dust means one of the 8 surrounding tiles will cause a cave-in, so you should avoid mining around it. if you mine a tile and there's no dust falling, you know that you can safely mine all 8 surrounding tiles. Sevenless thought of a nice trick: if you pave where you see dust falling you'll get a "map" of cave-in tiles which makes it very easy to avoid cave-ins without supports. i don't use supports anymore at all. of course you need a little luck the first time you start mining at a new spot, but cave-in tiles are not that common.
to give you some perspective, you can clearly see in this pic where i paved around the cave-in spots:
