[donjoe]

I always rent through some sort of AAA (automobile club). Almost each country does have a similar organization.

I do mostly rent my cars through ADAC (German AAA) which usually comes with unlimited miles, no excess insurance(s), young driver benefits, free additional driver, ... and a hotline which just 'works':

Hertz once charged a pretty extra on a prepaid rental. One call to ADAC complaining about the extra charge and I had my money back a week later.