Tonight I popped a DVD into my Mac Mini (Trope Trainer, because I needed to print something from it) and the machine declined to read it. On several tries with multiple discs I got either "can't read this; wanna eject?" or "hey, you gave me a blank disc" (um, no). Dani's iMac could read the original DVD just fine. Rebooting didn't change anything. So, off to the Internet for guidance.
I don't have a can of compressed air at home and advice was mixed about CD cleaning kits. One answer sounded unlikely, but it also seemed harmless so I gave it a shot.
And that is how I successfully cleaned my DVD drive with a microfiber cloth and a credit card. I should still get myself a can of air, though, because I probably only moved some dust particles around (and off the optic scanner). Nothing came out on the cloth, so whatever the problem was, it's still in there -- just, apparently, brushed aside.
Followup, in response to a question:
I found that suggestion here (post #3 from MattA). Not stated there: I oriented the card lengthwise (like if you're going to stick it into an ATM) and folded the microfiber cloth over the far end (so you need one that's roughly twice as long as your credit card). I was careful to only sweep in one direction; the last thing I wanted to do was rub some bit of grit back and forth across delicate machinery.
I didn't have any suitable alcohol in the house (this is not a job that calls for whiskey, y'know?), so I did it dry with a clean microfiber cloth. I use dry microfiber cloths on my glasses all the time, so I thought that'd be ok so long as I wasn't apply pressure.