When I ask locals for places to eat, I ask people who have no vested interest in where they send me, i.e, I don't ask the hotel, taxi drivers, or souvenir stands.

We were in Santa Cruz de Tenerife and wanted a good seafood restaurant that did not cater to tourists so I went into the Sony store near the hotel and asked one of the employees for a recommendation. His recommendation turned out to be one of the top meals of the trip, and one of the most inexpensive.