A 10 minutes walk from the metro Neptuno, Louta (a restaurant that is frequented by only those who…read morereally "know"), is what I would consider a picada -- despite the prices being somewhat high (similar to those in the Mercado Central) this restaurant, far from downtown has quality and service not seen anywhere else in Santiago.
I recommend ordering the Cancato de Salmon or "Reineta" or the Pastel de Jaiba (filled with cheesy goodness)
They have good daily lunch specials where executives from the surrounding areas come to pass their lunch hour.
They are known for having delicious empanadas, I recommend their empanada of cheese with shrimp -- seriously good!
Their fish is always fresh and Because they are so popular there are rumors that they are opening another restaurant close by.
The Louta is a great place for big family Sunday lunches and group outings.
Their decoration is simple and clean - especially great for families. The waiters are always super attentive - especially when you come with kids they will sometimes even give the kids a juice or treat to keep them entertained.
Tip: It is always full on any given day so call in the morning to make a reservation -- especially during the weekend.