I get inspiration at the oddest times - sometimes that's waking from a dream, sometimes that's in the shower, and often that's when driving. Something about driving seems to free up my mind to come up with tunes and lyrics!
But my memory ain't what it used to be - arguably, it was never that good - so how to save those fleeting moments of inspiration?
I find Evernote is the way to go. It caused me a bit of panic recently as the audio note option vanished, but it was still in there - they just removed it from the list of options that pops up when clicking the big plus to create a new note. No idea why, it's about the most useful thing in there to my mind, but you can add it back in the settings!
It's great because with a quick button press, no worse than changing radio stations on your car stereo, you can sing or hum away at your phone and never need lose a flash of insight again.
Best of all, once saved on one device, you can access it on any other - my Android phone, my iPad, and my PC can all see these notes, so when it comes time to work that initial idea into a song, I can get to it!