Time-boxing is an idea that I heard about a number of years ago. It's only been fairly recently that I have tried to incorporate it as a regular part of my daily workflow. The general idea behind time-boxing is that you concentrate on working for a set periods of time through-out the day. I adjust the period of time to how motivated I feel. When I feel really motivated I work in blocks of 25 minutes. When I am just getting started on the day I work in blocks of 10-15 minutes.