Regular taxi drivers in Frankfurt find their driver of choice and call him upfront every time they need a cab.

My taxi driver speaks fluent German and English (and probably French as well), has an impeccably clean car. Knows his way around town (including where to go eating, etc.) and always picks me up directly at the platform (on Frankfurt main station) or directly at the airport when I tell him the flight number and tell him whether I have checked luggage or travel with hand luggage only.

I will happily make a referral, if you send me a PM. Good service like this needs to be rewarded.