What do you when you need to concentrate?

Coffee
Eyedrop
Shower
Walking

There are many ways.
I came across two intriguing articles from NY times.

[First one] One college student who wanted to concentrate on test preparation, made up the symptom of ADHD to get prescription of its medicine. Becaming deeply addicted to that ADHD medicine which has as much addict level as cocaine, he started hallucinating and being aggressive, then commit suicide.

Link：http://www.nytimes.com/2013/02/03/us/concerns-about-adhd-practices-and-amphetamine-addiction.html?pagewanted=all&_r=0

[Second one] When you have so many things to do that you tend to overwork, you need to relax to become more productive. Time and Energy are finite. Energy, however, is rechargeable. Our concentration will last approx. 90 minutes, so we need to break. Especially, when you take a nap, the productivity will jump up.

Link)：http://www.nytimes.com/2013/02/10/opinion/sunday/relax-youll-be-more-productive.html

Ironically,
while there are more and more adults who rely on medicine like the first one
less and less adults pay attention to having a rest for more productivity.
The first article reminded me of “Limitless” – a movie in which one guy had a mysterious medicine which opened his brain’s potential to the maximum level. I liked it so much that I watched twice, but there is no such a thing as limitless.
Trailer “Limitless”

I suppose things are limited, that’s why they are precious.
What do you when you need to concentrate?
(I usually do hand-standing which helps me re-concentrate )