Are there any proven ways to increase concentration and focus? There are lots of popular articles out there giving listings of steps one can do to concentrate and focus better. But they seldom or never give links to studies that prove any of the steps work, at least to back up their lists.  

I want to know if science proved that any of the possible exercises, diets, behavior changes, etc. can do something positive for the concentration and focus? 

I don't have much access to certain studies, and I'm not even competent enough to read those science papers. So I need someone, who already read about this (so he/she knows where to look and isn't bothered much) to explain to me in plain english (not to plain) what can I do on my own to increase concentration and focus. What is proven to work. 

NOTE: Tag appropriately if needed. Thank you :)
Spark: The Revolutionary New Science of Exercise and the Brain details a number of studies that link exercise to concentration and students' results. The accompanying website is a good primer.