Generally in drupal modules are executed in as per the weight in the specified by the system table.
If two module has the same weight then modules are executed alphabetical order based on the name of module.
During working on one of my project, I was working with workflow module.
New version of workflow module adds Target State radio buttons on node form. I wanted to move these radio buttons to vertical tabs in node creation form.
I created a module for the form_alter function. I named my module as my_module.module.