Theming MENU_LOCAL_TASK

Hallo Everyone,

I'm a newbee to Drupal. I've been using D7 for my project and I've been struggling the a problem of
styling the primary and secondary menu tab. I actually need, that the tab link classes be derived
from the link content (href or title), so that I have the possibility to style them accordingly.

I know, that I should override the corresponding theme function, but I ve no idea where and what function
should I override. I would greatly appeciate a working example.

Thanks a lot!