How to choose a good scientific problem

"Choosing good problems is essential for being a good scientist. But what is a good problem, and how do you choose one?"
This is the incipit of the abstract of a nice article of Uri Arlon of the Weizmann Institute of Science.

Here is the link:http://download.cell.com/molecular-cell/pdf/PIIS1097276509006418.pdf?intermediate=true

Enjoy!