The brain is a wonderful organ; it starts working the moment you get up in the morning and does not stop until you get into the office.
I see productivity and focus as two distinct things, albeit interrelated. I believe it is possible to boost productivity with a somewhat minimal increase in the inherent focusing ability of a person. However, an increase in focus should in general lead to greater productivity, apart from other benefits. The Bhagvad Gita likens a persons senses to wild horses, and the mind is akin to the charioteer, who holds the reins of these horses. If you cannot rein in your senses, they will run wild and take you to places you don’t wish to go. Focus essentially boils down to the absolute control of your senses, which is why meditation helps so much in improving it. I’m sure lots of people don’t read long rambling answers (which this invariably will turn into), so getting to the gist of things, this is what i believe would help a lot (note that I’m trying not to mention things that already have been mentioned) :