I like Mark's suggested methods, but then they are similar to mine so its no big leap. I tend toward the habitual approach.
But really, it's ALL a habit, isn't it? I mean, the procrastination, mental road blocks, and excuses are just as habitual. Anything that can turn those habits around and into something more productive, exchange the habit of procrastinating with sitting down and writing, is worth doing. It may take several tries, and will be different solutions for different people, but the end goal is the same. You have to remove your excuses.
When I started my novel, I had just come off a job and had the whole day to write, but when I sat down to do it, I was distracted by everthing that needed to be done around the house too. If there were dishes in the sink, laundry piled up, the lawn unmowed, etc., it was distracting enough to keep me from focusing on the book. So after a time of struggling with it, I simply set aside a week and did all the other stuff: spring cleaned the house, tidied the yard, organized every drawer and bookshelf, etc. When I was all done, I sat down to write. Suddenly I could do it. For me, removing all those stupid little distractions actually worked. Those things were my excuse, so I removed the excuse.
I especially appreciate Mark's time at the desk target balancing the word target. I'm not as in love with word targets, especially daily ones. Longer term ones, okay, those work for me. You have to aim at something tangible. However, there are days when I write less but say more, and then there are days when I write a bunch of stuff that's crap and it simply gets tossed. I prefer more of the former than the latter.