The one thing that really improved my productivity was actually really simple. First of all, eliminate objects in your neighborhood; physical as well as virtual objects. Next to this, you should plan ahead. Planning is essential to any organizing process. You will always know what you did and what you should do next, which will certainly improve productivity. As bartonfink notes, write things down on paper. Then make a plan out of it and subsequently extract specific tasks.
Of course, one main requirement is that you should be passionate about your work and focus on your core tasks. Then again, you should plan clearly and write down your short and long time goals. I reckon this works for almost everyone.