Would in the past
Would is often used where the pretérito imperfecto would be in Spanish. Unlike used to, would should only be used with action verbs rather than state verbs.
Context or an adverb are helpful so as not to confuse it with the conditional.
My grandfather would often read to me when I was younger --Mi abuelo me leía a menudo cuando era pequeño
I would say yes to everything (ambiguous!) -- Yo diría/decía?? que sí a todo
When I was asked for help, I would say yes to everything -- Cuando me pedían ayuda yo decía que sí a todo.(diría no pega aquí)
I used to (would) live in the UK -- Vivía en el Reino Unido
Would can also be used to express willingness and propensity to do something. In the present we use will.
He wouldn't help me -- Se negó a ayudarme / No quiso ayudarme
-Grandpa complained again. - He would, wouldn't he -- El abuelo se quejó otra vez. -Claro. No podía ser de otra forma