Since many of us are suffering from the same problem (lack of time to write) and it's becoming evident that no one's going to write an article about it, I thought we might as well share our ideas, especially the ones that work.
As you may have noticed, I've managed to make myself some time to write today, so I'll post what's worked for me so far. Post your own ideas and experiences, and maybe we'll be able to help each other and bring more writings to this forum.
My advice is oriented to early risers because I am one, but if you're nocturnal (or vespertine) you may find a way to adjust it to your schedule. If so, feel free to post it here.
1. Think of what to write whenever you can, no matter if there are no writing implements at hand. The bus is a good place for that, or any other situation in which you have idle time. The important bits will stay. Try to remember any good ideas you've had. If you can take notes, do so (and remember when you keep them).
2. Save a day for writing, up to a week in advance. Make sure you have no compromises for that day. Arrange all your other tasks as if that day didn't exist.
3. On the eve of the chosen day, go to bed early, thinking of your story. Keep in mind that the following morning, you're going to write it.
4. On the morning of the chosen day, get up as early as possible. Go through your previous chapter, or a previous story if it's a one-shot, to get in the mood. Don't do anything that might take your mind away from writing, but do allow yourself to do things that can help you. In my case, many cups of tea do the trick. Write as much as you can before anyone else wakes up. After that, if you still need time, you can try to negotiate to be left alone for a while. If it fails, you can always repeat from step one. At least you'll have written something and you can continue it next time.
...And that's what I've just done. That's how chapter 31 of Quest of Twelve was written and chapter 30 was posted. Any other ideas?
(Edit note: funny how I was the first one to request this and now I'm the first one to provide it.)