Best way to learn Magento

[Keith Smith]

Hi,

I need to become a Magento developer.  I've installed it on Ubuntu 14.04 
and have read a lot of the user manual.  I've read some of the developer 
docs as well.  I need to understand how to build modules, modify themes, 
and probably need to know about their hooks.  I used Build a Module to 
learn Drupal.  Wish I could find something like that for Magento.

What is the best way to become a Magento developer?

Thanks!

Keith