How to reclaim space on an Apple Mac's storage/disk

As 'how to's go, this one's really, really simple. But worth documenting, as it has me scratching my head every time. So your Macbook's SSD is filling up and you've had a bit of a spring clean. Gone are all those temporary video and audio files, those duplicate folders of images, and so on. You've deleted, say, 15GB, but... the free space shown in Finder is exactly the same. OK, you think, empty the (recycle) 'bin'. That'll do it. Nope, the free space stays resolutely where it was before you started your clear-out. So what's going on? It turns out that emptying the 'bin' actually did delete the files permanently, but that Mac OS has a wealth of checks and tidying up procedures that it needs to do under the hood before it's happy to declare the space genuinely freed up. So the answer to the 'how to', after all your deleting and bin-emptying, is... Wait! Leave your Mac on, feel free to keep on working and doing what you normall...