Beyond estar: the gerund periphrases that add colour and precision
Ir + gerundio paints an action unfolding little by little — a nuance English needs adverbs for.
Voy entendiendo la gramática. (I'm gradually getting the grammar.)
El cielo se va oscureciendo. (The sky is slowly darkening.)
Ve preparando la cena, ahora llego. (Start getting dinner ready, I'm on my way.)
Ir + gerundio = progressive build-up. The imperative ve preparando = "start ...ing (in the meantime)".
Andar + gerundio adds a flavour of "going around doing something" — often with a hint of disapproval.
Anda diciendo que fue idea suya. (He's going around saying it was his idea.)
¿Qué andas buscando? (What are you after / poking around for?)
Colloquial and very Spanish — recognise it in speech, deploy it carefully.
You know llevar + time + gerundio (have been doing). Its negative twin is llevar + time + sin + infinitive.
Llevo tres años estudiando español. (I've been studying Spanish for three years.)
Llevo dos meses sin fumar. (I haven't smoked for two months.)
"I haven't done X for [time]" → llevo + tiempo + sin + infinitive. No perfect tense needed.
Continuation and lingering: seguir + gerundio (still doing) and quedarse + gerundio (stay doing).
Sigue lloviendo. (It's still raining.)
Me quedé estudiando hasta las dos. (I stayed up studying until two.)
Negative of seguir: ya no + verb — Ya no llueve (it's not raining any more), or sigue sin llover (it still hasn't rained).
English -ing spreads everywhere; the Spanish gerund doesn't. Three no-go zones:
Subject: Fumar es malo. (not "fumando")
After prepositions: antes de salir (not "saliendo")
As adjective: agua corriente, una historia fascinante (not gerunds!)
"The man reading the paper" → el hombre que lee el periódico. Spanish prefers a relative clause.
Traps for English speakers
These are the errors English speakers make most often.