How does Hiruma get all the information in his black book?
The information were gathered using hacked cameras, mostly in cellphones. The hacked network was that great, that he could get information of nearly anything in Tokyo, and he never stopped that network.

Funfact:  


  In one of Q&amp;A column, it is revealed that the book was actually blank- All the information lies within Hiruma's brain, and the book only serves as a threat tool.


Source: Eyeshield 21 Wiki