Most of the time I've been in Europe, it hasn't been as a tourist, but rather as an expat living/working there for months at a time. So in most cases, the restaurants I've gone to, I've been taken there by my local friends/colleagues. That's a pretty fantastic way to do it. Nothing but great experiences.
I've also been as a tourist and when I haven't been able to grab a recommendation from a nearby local friend, I've found that some of the guidebooks have great advice. Rick Steves never steered me wrong, and another lesser-known one, I think Lonely Planet, also had some good recommendations.
I've never used travel apps because the masses are stupid and make stupid recommendations in general.