Ordering a small beer like a local

Una caña

OO-nah KAH-nyah — A small draft beer (Spain)

"Una caña, por favor."
A small draft beer, please.

The default beer order in Spain — smaller than a pint on purpose, so it stays cold, and ordering one instead of a full pint instantly reads as local rather than tourist.

"My order. Every single time, at every single bar."— Graciela