[TYPO3-english] How do I specify a default action?

[Calgacus map Brude]

I made a new extension in extension builder (a basic 4 model extension with no custom work in it, the only thing slightly fancy it does is extend the fe_users table) and installed it and made a page with the plugin and when I view the page I get a blank area where the plugin should appear - not a whole blank page just the part where the plugin should appear. I put some 
echo __FUNCTION__.__LINE__;
die; 
lines in all the listActions so if I was hitting any of them I'd at least know which I was hitting. But I see no echo lines and I clearly never hit a die; so I guess my extension is not hitting any action, maybe because I have to specify one as the default. My extension has 4 models. How do I specify what action gets called? 
I am using typo3 v4.5.30 with extbase.

Thanks