On the Templates or Triggers settings page, you'll see a checkbox next to each template or trigger. When you check the template or trigger you want to delete, you will see a Delete button appear at the top. Just click that Delete button.
If there are messages associated with the trigger, you won't be able to delete the trigger. Instead, you can disable the trigger by going in to the trigger and scrolling all the way to the bottom of the screen. You'll see a Status Enabled checkbox. If you uncheck the box, the trigger will be disabled and won't show up by default in the listing of all active triggers.
