I think that I first learned of the idea of 'parking on a downhill slope' via 43folders. Merlin passed on the advice from Jeffrey Windsor (which he, in turn, got from a book on finishing your dissertation) that you should try to end the day's work by setting out very clearly where you need to start the next day. I've tried to follow that advice, but I don't do it as often as I should. However, today I made a concerted effort.
I've got to write a reference for a student; it's not a particularly difficult job, but it's one of those things you procrastinate over and find difficult to start. By the time I'd got all my other stuff done today, it was getting late and I was exhausted. I wanted to make a start on the reference, because I knew if I didn't that I'd be in exactly the same Procrast-A-Rama state that I'm in today. But I couldn't write the reference because I was too tired to do a good job on it, and I didn't have time.
The answer, I decided, was to park downhill, and nibble away at the task a bit. I created a folder on my computer to hold the reference (and the inevitable future ones for that student), looked up and noted down the student's marks for the previous years, addressed the envelope for the finished reference, and finally made a few notes in a file as phrases occurred to me. Each thing in itself was pretty trivial, but now I've got everything gathered together that I'll need to finish the task, and I've made an important psychological start, at least. Of course, the real proof of whether this technique works or not will come tomorrow when I'll take the hand-brake off and see whether I roll downhill as I want to, or defy the laws of physics and roll back uphill.