How can I output debug info from hook_node_presave()? I'm learning about module design for Drupal 7 and I want to see what hook_node_presave is being passed (and working with), how can I output debug info so that I can learn how to manipulate it?

Is there a similar hook that I can use to print out debug info?
install the devel module and dump your variables with dpm($input, $name = NULL) to the screen.

This article shows additional debugging options.