CMS Made Simple Forums

1) split your install/upgrade/uninstall into method.xxxxxx.php
2) split your actions into action.xxxxxx.php
3) split your events into event.xxxxxx.php
4) I split my admin tabs into seperate files using function.admin_tab_xxxxx.php or something like that
5) then I try to use classes
    when I found that I'm going to be re-using those classes or functions I created an addon module for just that stuff CGExtensions

I think the best module to look at would be Questions, it's pretty clean and well organized.

Typically though, I don't call one action from another, I use redirects to hande the flow.