I've read about business people using an "egg timer" to help them stay focused and on task throughout the day. (It's not really my idea of an egg timer. When I think of an egg timer I think of a mini "hourglass" timer with enough sand in it for only three minutes.)
The way it works is that you set the timer for 25 minutes. Get to work on a project and don't allow distractions until the timer goes off. After the timer goes off, get up and move around. Take no more than a five minute break and then set the timer for 25 minutes and get back to focused work.
Today I decided to put the idea to work with a twist. As soon as the timer goes off (and I can break away from writing a sentence or finish a thought related to the task at hand), get up and do just a minute of exercise with light weights. Then grab a glass of water or do whatever else makes sense during the break and then get back to work.
So far this afternoon I am much more focused and energetic than I normally am at 1:30 PM. I think this may go a long, LONG way toward increasing my productivity.