I like to throw some pomodoros in each day. I feel that at first it is a tad awkward. However, after you get used to it, you feel the need to really finish a unit of work in the allotted time. I feel that the pressure to get into the zone quick and practicing it helps. For those unfamiliar: pomodoro is 25 minutes uninterrupted work, 5 minutes break. Rinse, repeat.