Art Of Manliness with 11 exercises that you can use to train your powers of concentration:
Research has shown that individuals who can sustain their attention for long periods of time perform better on all sorts of cognitive challenges than those who cannot. A man with a scatter-shot attention span will only be able to experience one plane of existence; he can skim across the surface of the world’s vast knowledge and wisdom, but is unable to dive deeper and discover the treasures below. The man with an iron-clad focus can do both; he is the boat captain and the pearl diver and the world is truly his oyster.
If you have a goal to learn and understand as much about the world as you possibly can before you die, strengthening your power of concentration is not an option, it’s a necessity.